DEFINITION pr2_gen_abbr()
TYPE =
       c:C
         .u1:T
           .t1:T
             .x:T
               .pr2 c (THead (Bind Abbr) u1 t1) x
                 (or
                      ex3_2
                        T
                        T
                        λu2:T.λt2:T.eq T x (THead (Bind Abbr) u2 t2)
                        λu2:T.λ:T.pr2 c u1 u2
                        λ:T
                          .λt2:T
                            .or3
                              b:B.u:T.(pr2 (CHead c (Bind b) u) t1 t2)
                              ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c (Bind Abbr) u) t1 t2
                              ex3_2
                                T
                                T
                                λy:T.λ:T.pr2 (CHead c (Bind Abbr) u1) t1 y
                                λy:T.λz:T.pr0 y z
                                λ:T.λz:T.pr2 (CHead c (Bind Abbr) u1) z t2
                      b:B.u:T.(pr2 (CHead c (Bind b) u) t1 (lift (S OO x)))
BODY =
        assume cC
        assume u1T
        assume t1T
        assume xT
        suppose Hpr2 c (THead (Bind Abbr) u1 t1) x
           assume yT
           suppose H0pr2 c y x
             we proceed by induction on H0 to prove 
                eq T y (THead (Bind Abbr) u1 t1)
                  (or
                       ex3_2
                         T
                         T
                         λu2:T.λt2:T.eq T x (THead (Bind Abbr) u2 t2)
                         λu2:T.λ:T.pr2 c u1 u2
                         λ:T
                           .λt2:T
                             .or3
                               b:B.u:T.(pr2 (CHead c (Bind b) u) t1 t2)
                               ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c (Bind Abbr) u) t1 t2
                               ex3_2
                                 T
                                 T
                                 λy0:T.λ:T.pr2 (CHead c (Bind Abbr) u1) t1 y0
                                 λy0:T.λz:T.pr0 y0 z
                                 λ:T.λz:T.pr2 (CHead c (Bind Abbr) u1) z t2
                       b:B.u:T.(pr2 (CHead c (Bind b) u) t1 (lift (S OO x)))
                case pr2_free : c0:C t0:T t2:T H1:pr0 t0 t2 
                   the thesis becomes 
                   H2:eq T t0 (THead (Bind Abbr) u1 t1)
                     .or
                       ex3_2
                         T
                         T
                         λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3)
                         λu2:T.λ:T.pr2 c0 u1 u2
                         λ:T
                           .λt3:T
                             .or3
                               b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                               ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                               ex3_2
                                 T
                                 T
                                 λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                 λy0:T.λz:T.pr0 y0 z
                                 λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                       b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2))
                      suppose H2eq T t0 (THead (Bind Abbr) u1 t1)
                         (H3
                            we proceed by induction on H2 to prove pr0 (THead (Bind Abbr) u1 t1) t2
                               case refl_equal : 
                                  the thesis becomes the hypothesis H1
pr0 (THead (Bind Abbr) u1 t1) t2
                         end of H3
                         by (pr0_gen_abbr . . . H3)
                         we proved 
                            or
                              ex3_2
                                T
                                T
                                λu2:T.λt2:T.eq T t2 (THead (Bind Abbr) u2 t2)
                                λu2:T.λ:T.pr0 u1 u2
                                λu2:T.λt2:T.or (pr0 t1 t2) (ex2 T λy:T.pr0 t1 y λy:T.subst0 O u2 y t2)
                              pr0 t1 (lift (S OO t2)
                         we proceed by induction on the previous result to prove 
                            or
                              ex3_2
                                T
                                T
                                λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3)
                                λu2:T.λ:T.pr2 c0 u1 u2
                                λ:T
                                  .λt3:T
                                    .or3
                                      b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                      ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                      ex3_2
                                        T
                                        T
                                        λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                        λy0:T.λz:T.pr0 y0 z
                                        λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                              b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2))
                            case or_introl : H4:ex3_2 T T λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3) λu2:T.λ:T.pr0 u1 u2 λu2:T.λt3:T.or (pr0 t1 t3) (ex2 T λy0:T.pr0 t1 y0 λy0:T.subst0 O u2 y0 t3) 
                               the thesis becomes 
                               or
                                 ex3_2
                                   T
                                   T
                                   λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3)
                                   λu2:T.λ:T.pr2 c0 u1 u2
                                   λ:T
                                     .λt3:T
                                       .or3
                                         b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                         ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                         ex3_2
                                           T
                                           T
                                           λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                           λy0:T.λz:T.pr0 y0 z
                                           λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                 b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2))
                                  we proceed by induction on H4 to prove 
                                     or
                                       ex3_2
                                         T
                                         T
                                         λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3)
                                         λu2:T.λ:T.pr2 c0 u1 u2
                                         λ:T
                                           .λt3:T
                                             .or3
                                               b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                               ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                               ex3_2
                                                 T
                                                 T
                                                 λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                 λy0:T.λz:T.pr0 y0 z
                                                 λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                       b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2))
                                     case ex3_2_intro : x0:T x1:T H5:eq T t2 (THead (Bind Abbr) x0 x1) H6:pr0 u1 x0 H_x:or (pr0 t1 x1) (ex2 T λy0:T.pr0 t1 y0 λy0:T.subst0 O x0 y0 x1) 
                                        the thesis becomes 
                                        or
                                          ex3_2
                                            T
                                            T
                                            λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3)
                                            λu2:T.λ:T.pr2 c0 u1 u2
                                            λ:T
                                              .λt3:T
                                                .or3
                                                  b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                                  ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                                  ex3_2
                                                    T
                                                    T
                                                    λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                    λy0:T.λz:T.pr0 y0 z
                                                    λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                          b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2))
                                           we proceed by induction on H_x to prove 
                                              or
                                                ex3_2
                                                  T
                                                  T
                                                  λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3)
                                                  λu2:T.λ:T.pr2 c0 u1 u2
                                                  λ:T
                                                    .λt3:T
                                                      .or3
                                                        b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                                        ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                                        ex3_2
                                                          T
                                                          T
                                                          λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                          λy0:T.λz:T.pr0 y0 z
                                                          λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2))
                                              case or_introl : H7:pr0 t1 x1 
                                                 the thesis becomes 
                                                 or
                                                   ex3_2
                                                     T
                                                     T
                                                     λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3)
                                                     λu2:T.λ:T.pr2 c0 u1 u2
                                                     λ:T
                                                       .λt3:T
                                                         .or3
                                                           b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                                           ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                                           ex3_2
                                                             T
                                                             T
                                                             λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                             λy0:T.λz:T.pr0 y0 z
                                                             λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                   b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2))
                                                    (h1
                                                       by (refl_equal . .)
eq T (THead (Bind Abbr) x0 x1) (THead (Bind Abbr) x0 x1)
                                                    end of h1
                                                    (h2by (pr2_free . . . H6) we proved pr2 c0 u1 x0
                                                    (h3
                                                        assume bB
                                                        assume uT
                                                          by (pr2_free . . . H7)
                                                          we proved pr2 (CHead c0 (Bind b) u) t1 x1
                                                       we proved b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 x1)
                                                       by (or3_intro0 . . . previous)

                                                          or3
                                                            b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 x1)
                                                            ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 x1
                                                            ex3_2
                                                              T
                                                              T
                                                              λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                              λy0:T.λz:T.pr0 y0 z
                                                              λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z x1
                                                    end of h3
                                                    by (ex3_2_intro . . . . . . . h1 h2 h3)
                                                    we proved 
                                                       ex3_2
                                                         T
                                                         T
                                                         λu2:T.λt3:T.eq T (THead (Bind Abbr) x0 x1) (THead (Bind Abbr) u2 t3)
                                                         λu2:T.λ:T.pr2 c0 u1 u2
                                                         λ:T
                                                           .λt3:T
                                                             .or3
                                                               b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                                               ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                                               ex3_2
                                                                 T
                                                                 T
                                                                 λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                 λy0:T.λz:T.pr0 y0 z
                                                                 λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                    by (or_introl . . previous)
                                                    we proved 
                                                       or
                                                         ex3_2
                                                           T
                                                           T
                                                           λu2:T.λt3:T.eq T (THead (Bind Abbr) x0 x1) (THead (Bind Abbr) u2 t3)
                                                           λu2:T.λ:T.pr2 c0 u1 u2
                                                           λ:T
                                                             .λt3:T
                                                               .or3
                                                                 b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                                                 ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                                                 ex3_2
                                                                   T
                                                                   T
                                                                   λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                   λy0:T.λz:T.pr0 y0 z
                                                                   λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                         b:B
                                                           .u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO (THead (Bind Abbr) x0 x1)))
                                                    by (eq_ind_r . . . previous . H5)

                                                       or
                                                         ex3_2
                                                           T
                                                           T
                                                           λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3)
                                                           λu2:T.λ:T.pr2 c0 u1 u2
                                                           λ:T
                                                             .λt3:T
                                                               .or3
                                                                 b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                                                 ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                                                 ex3_2
                                                                   T
                                                                   T
                                                                   λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                   λy0:T.λz:T.pr0 y0 z
                                                                   λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                         b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2))
                                              case or_intror : H_x0:ex2 T λy0:T.pr0 t1 y0 λy0:T.subst0 O x0 y0 x1 
                                                 the thesis becomes 
                                                 or
                                                   ex3_2
                                                     T
                                                     T
                                                     λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3)
                                                     λu2:T.λ:T.pr2 c0 u1 u2
                                                     λ:T
                                                       .λt3:T
                                                         .or3
                                                           b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                                           ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                                           ex3_2
                                                             T
                                                             T
                                                             λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                             λy0:T.λz:T.pr0 y0 z
                                                             λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                   b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2))
                                                    we proceed by induction on H_x0 to prove 
                                                       or
                                                         ex3_2
                                                           T
                                                           T
                                                           λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3)
                                                           λu2:T.λ:T.pr2 c0 u1 u2
                                                           λ:T
                                                             .λt3:T
                                                               .or3
                                                                 b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                                                 ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                                                 ex3_2
                                                                   T
                                                                   T
                                                                   λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                   λy0:T.λz:T.pr0 y0 z
                                                                   λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                         b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2))
                                                       case ex_intro2 : x2:T H7:pr0 t1 x2 H8:subst0 O x0 x2 x1 
                                                          the thesis becomes 
                                                          or
                                                            ex3_2
                                                              T
                                                              T
                                                              λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3)
                                                              λu2:T.λ:T.pr2 c0 u1 u2
                                                              λ:T
                                                                .λt3:T
                                                                  .or3
                                                                    b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                                                    ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                                                    ex3_2
                                                                      T
                                                                      T
                                                                      λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                      λy0:T.λz:T.pr0 y0 z
                                                                      λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                            b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2))
                                                             by (pr0_subst0_back . . . . H8 . H6)
                                                             we proved ex2 T λt:T.subst0 O u1 x2 t λt:T.pr0 t x1
                                                             we proceed by induction on the previous result to prove 
                                                                or
                                                                  ex3_2
                                                                    T
                                                                    T
                                                                    λu2:T.λt3:T.eq T (THead (Bind Abbr) x0 x1) (THead (Bind Abbr) u2 t3)
                                                                    λu2:T.λ:T.pr2 c0 u1 u2
                                                                    λ:T
                                                                      .λt3:T
                                                                        .or3
                                                                          b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                                                          ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                                                          ex3_2
                                                                            T
                                                                            T
                                                                            λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                            λy0:T.λz:T.pr0 y0 z
                                                                            λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                  b:B
                                                                    .u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO (THead (Bind Abbr) x0 x1)))
                                                                case ex_intro2 : x3:T :subst0 O u1 x2 x3 :pr0 x3 x1 
                                                                   the thesis becomes 
                                                                   or
                                                                     ex3_2
                                                                       T
                                                                       T
                                                                       λu2:T.λt3:T.eq T (THead (Bind Abbr) x0 x1) (THead (Bind Abbr) u2 t3)
                                                                       λu2:T.λ:T.pr2 c0 u1 u2
                                                                       λ:T
                                                                         .λt3:T
                                                                           .or3
                                                                             b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                                                             ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                                                             ex3_2
                                                                               T
                                                                               T
                                                                               λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                               λy0:T.λz:T.pr0 y0 z
                                                                               λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                     b:B
                                                                       .u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO (THead (Bind Abbr) x0 x1)))
                                                                      (h1
                                                                         by (refl_equal . .)
eq T (THead (Bind Abbr) x0 x1) (THead (Bind Abbr) x0 x1)
                                                                      end of h1
                                                                      (h2by (pr2_free . . . H6) we proved pr2 c0 u1 x0
                                                                      (h3
                                                                         by (getl_refl . . .)
                                                                         we proved getl O (CHead c0 (Bind Abbr) x0) (CHead c0 (Bind Abbr) x0)
                                                                         by (pr2_delta . . . . previous . . H7 . H8)
                                                                         we proved pr2 (CHead c0 (Bind Abbr) x0) t1 x1
                                                                         by (ex_intro2 . . . . H6 previous)
                                                                         we proved ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 x1
                                                                         by (or3_intro1 . . . previous)

                                                                            or3
                                                                              b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 x1)
                                                                              ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 x1
                                                                              ex3_2
                                                                                T
                                                                                T
                                                                                λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                λy0:T.λz:T.pr0 y0 z
                                                                                λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z x1
                                                                      end of h3
                                                                      by (ex3_2_intro . . . . . . . h1 h2 h3)
                                                                      we proved 
                                                                         ex3_2
                                                                           T
                                                                           T
                                                                           λu2:T.λt3:T.eq T (THead (Bind Abbr) x0 x1) (THead (Bind Abbr) u2 t3)
                                                                           λu2:T.λ:T.pr2 c0 u1 u2
                                                                           λ:T
                                                                             .λt3:T
                                                                               .or3
                                                                                 b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                                                                 ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                                                                 ex3_2
                                                                                   T
                                                                                   T
                                                                                   λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                   λy0:T.λz:T.pr0 y0 z
                                                                                   λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                      by (or_introl . . previous)

                                                                         or
                                                                           ex3_2
                                                                             T
                                                                             T
                                                                             λu2:T.λt3:T.eq T (THead (Bind Abbr) x0 x1) (THead (Bind Abbr) u2 t3)
                                                                             λu2:T.λ:T.pr2 c0 u1 u2
                                                                             λ:T
                                                                               .λt3:T
                                                                                 .or3
                                                                                   b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                                                                   ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                                                                   ex3_2
                                                                                     T
                                                                                     T
                                                                                     λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                     λy0:T.λz:T.pr0 y0 z
                                                                                     λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                           b:B
                                                                             .u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO (THead (Bind Abbr) x0 x1)))
                                                             we proved 
                                                                or
                                                                  ex3_2
                                                                    T
                                                                    T
                                                                    λu2:T.λt3:T.eq T (THead (Bind Abbr) x0 x1) (THead (Bind Abbr) u2 t3)
                                                                    λu2:T.λ:T.pr2 c0 u1 u2
                                                                    λ:T
                                                                      .λt3:T
                                                                        .or3
                                                                          b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                                                          ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                                                          ex3_2
                                                                            T
                                                                            T
                                                                            λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                            λy0:T.λz:T.pr0 y0 z
                                                                            λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                  b:B
                                                                    .u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO (THead (Bind Abbr) x0 x1)))
                                                             by (eq_ind_r . . . previous . H5)

                                                                or
                                                                  ex3_2
                                                                    T
                                                                    T
                                                                    λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3)
                                                                    λu2:T.λ:T.pr2 c0 u1 u2
                                                                    λ:T
                                                                      .λt3:T
                                                                        .or3
                                                                          b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                                                          ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                                                          ex3_2
                                                                            T
                                                                            T
                                                                            λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                            λy0:T.λz:T.pr0 y0 z
                                                                            λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                  b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2))

                                                       or
                                                         ex3_2
                                                           T
                                                           T
                                                           λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3)
                                                           λu2:T.λ:T.pr2 c0 u1 u2
                                                           λ:T
                                                             .λt3:T
                                                               .or3
                                                                 b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                                                 ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                                                 ex3_2
                                                                   T
                                                                   T
                                                                   λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                   λy0:T.λz:T.pr0 y0 z
                                                                   λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                         b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2))

                                              or
                                                ex3_2
                                                  T
                                                  T
                                                  λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3)
                                                  λu2:T.λ:T.pr2 c0 u1 u2
                                                  λ:T
                                                    .λt3:T
                                                      .or3
                                                        b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                                        ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                                        ex3_2
                                                          T
                                                          T
                                                          λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                          λy0:T.λz:T.pr0 y0 z
                                                          λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2))

                                     or
                                       ex3_2
                                         T
                                         T
                                         λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3)
                                         λu2:T.λ:T.pr2 c0 u1 u2
                                         λ:T
                                           .λt3:T
                                             .or3
                                               b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                               ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                               ex3_2
                                                 T
                                                 T
                                                 λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                 λy0:T.λz:T.pr0 y0 z
                                                 λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                       b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2))
                            case or_intror : H4:pr0 t1 (lift (S OO t2) 
                               the thesis becomes 
                               or
                                 ex3_2
                                   T
                                   T
                                   λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3)
                                   λu2:T.λ:T.pr2 c0 u1 u2
                                   λ:T
                                     .λt3:T
                                       .or3
                                         b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                         ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                         ex3_2
                                           T
                                           T
                                           λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                           λy0:T.λz:T.pr0 y0 z
                                           λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                 b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2))
                                   assume bB
                                   assume uT
                                     by (pr2_free . . . H4)
                                     we proved pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2)
                                  we proved b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2))
                                  by (or_intror . . previous)

                                     or
                                       ex3_2
                                         T
                                         T
                                         λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3)
                                         λu2:T.λ:T.pr2 c0 u1 u2
                                         λ:T
                                           .λt3:T
                                             .or3
                                               b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                               ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                               ex3_2
                                                 T
                                                 T
                                                 λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                 λy0:T.λz:T.pr0 y0 z
                                                 λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                       b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2))
                         we proved 
                            or
                              ex3_2
                                T
                                T
                                λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3)
                                λu2:T.λ:T.pr2 c0 u1 u2
                                λ:T
                                  .λt3:T
                                    .or3
                                      b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                      ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                      ex3_2
                                        T
                                        T
                                        λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                        λy0:T.λz:T.pr0 y0 z
                                        λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                              b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2))

                         H2:eq T t0 (THead (Bind Abbr) u1 t1)
                           .or
                             ex3_2
                               T
                               T
                               λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3)
                               λu2:T.λ:T.pr2 c0 u1 u2
                               λ:T
                                 .λt3:T
                                   .or3
                                     b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 t3)
                                     ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c0 (Bind Abbr) u) t1 t3
                                     ex3_2
                                       T
                                       T
                                       λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                       λy0:T.λz:T.pr0 y0 z
                                       λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                             b:B.u:T.(pr2 (CHead c0 (Bind b) u) t1 (lift (S OO t2))
                case pr2_delta : c0:C d:C u:T i:nat H1:getl i c0 (CHead d (Bind Abbr) u) t0:T t2:T H2:pr0 t0 t2 t:T H3:subst0 i u t2 t 
                   the thesis becomes 
                   H4:eq T t0 (THead (Bind Abbr) u1 t1)
                     .or
                       ex3_2
                         T
                         T
                         λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                         λu2:T.λ:T.pr2 c0 u1 u2
                         λ:T
                           .λt3:T
                             .or3
                               b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                               ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                               ex3_2
                                 T
                                 T
                                 λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                 λy0:T.λz:T.pr0 y0 z
                                 λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                       b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                      suppose H4eq T t0 (THead (Bind Abbr) u1 t1)
                         (H5
                            we proceed by induction on H4 to prove pr0 (THead (Bind Abbr) u1 t1) t2
                               case refl_equal : 
                                  the thesis becomes the hypothesis H2
pr0 (THead (Bind Abbr) u1 t1) t2
                         end of H5
                         by (pr0_gen_abbr . . . H5)
                         we proved 
                            or
                              ex3_2
                                T
                                T
                                λu2:T.λt2:T.eq T t2 (THead (Bind Abbr) u2 t2)
                                λu2:T.λ:T.pr0 u1 u2
                                λu2:T.λt2:T.or (pr0 t1 t2) (ex2 T λy:T.pr0 t1 y λy:T.subst0 O u2 y t2)
                              pr0 t1 (lift (S OO t2)
                         we proceed by induction on the previous result to prove 
                            or
                              ex3_2
                                T
                                T
                                λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                λu2:T.λ:T.pr2 c0 u1 u2
                                λ:T
                                  .λt3:T
                                    .or3
                                      b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                      ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                      ex3_2
                                        T
                                        T
                                        λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                        λy0:T.λz:T.pr0 y0 z
                                        λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                              b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                            case or_introl : H6:ex3_2 T T λu2:T.λt3:T.eq T t2 (THead (Bind Abbr) u2 t3) λu2:T.λ:T.pr0 u1 u2 λu2:T.λt3:T.or (pr0 t1 t3) (ex2 T λy0:T.pr0 t1 y0 λy0:T.subst0 O u2 y0 t3) 
                               the thesis becomes 
                               or
                                 ex3_2
                                   T
                                   T
                                   λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                   λu2:T.λ:T.pr2 c0 u1 u2
                                   λ:T
                                     .λt3:T
                                       .or3
                                         b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                         ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                         ex3_2
                                           T
                                           T
                                           λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                           λy0:T.λz:T.pr0 y0 z
                                           λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                 b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                  we proceed by induction on H6 to prove 
                                     or
                                       ex3_2
                                         T
                                         T
                                         λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                         λu2:T.λ:T.pr2 c0 u1 u2
                                         λ:T
                                           .λt3:T
                                             .or3
                                               b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                               ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                               ex3_2
                                                 T
                                                 T
                                                 λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                 λy0:T.λz:T.pr0 y0 z
                                                 λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                       b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                     case ex3_2_intro : x0:T x1:T H7:eq T t2 (THead (Bind Abbr) x0 x1) H8:pr0 u1 x0 H_x:or (pr0 t1 x1) (ex2 T λy0:T.pr0 t1 y0 λy0:T.subst0 O x0 y0 x1) 
                                        the thesis becomes 
                                        or
                                          ex3_2
                                            T
                                            T
                                            λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                            λu2:T.λ:T.pr2 c0 u1 u2
                                            λ:T
                                              .λt3:T
                                                .or3
                                                  b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                  ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                  ex3_2
                                                    T
                                                    T
                                                    λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                    λy0:T.λz:T.pr0 y0 z
                                                    λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                          b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                           we proceed by induction on H_x to prove 
                                              or
                                                ex3_2
                                                  T
                                                  T
                                                  λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                  λu2:T.λ:T.pr2 c0 u1 u2
                                                  λ:T
                                                    .λt3:T
                                                      .or3
                                                        b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                        ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                        ex3_2
                                                          T
                                                          T
                                                          λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                          λy0:T.λz:T.pr0 y0 z
                                                          λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                              case or_introl : H9:pr0 t1 x1 
                                                 the thesis becomes 
                                                 or
                                                   ex3_2
                                                     T
                                                     T
                                                     λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                     λu2:T.λ:T.pr2 c0 u1 u2
                                                     λ:T
                                                       .λt3:T
                                                         .or3
                                                           b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                           ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                           ex3_2
                                                             T
                                                             T
                                                             λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                             λy0:T.λz:T.pr0 y0 z
                                                             λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                   b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                    (H10
                                                       we proceed by induction on H7 to prove subst0 i u (THead (Bind Abbr) x0 x1) t
                                                          case refl_equal : 
                                                             the thesis becomes the hypothesis H3
subst0 i u (THead (Bind Abbr) x0 x1) t
                                                    end of H10
                                                    by (subst0_gen_head . . . . . . H10)
                                                    we proved 
                                                       or3
                                                         ex2 T λu2:T.eq T t (THead (Bind Abbr) u2 x1) λu2:T.subst0 i u x0 u2
                                                         ex2 T λt2:T.eq T t (THead (Bind Abbr) x0 t2) λt2:T.subst0 (s (Bind Abbr) i) u x1 t2
                                                         ex3_2
                                                           T
                                                           T
                                                           λu2:T.λt2:T.eq T t (THead (Bind Abbr) u2 t2)
                                                           λu2:T.λ:T.subst0 i u x0 u2
                                                           λ:T.λt2:T.subst0 (s (Bind Abbr) i) u x1 t2
                                                    we proceed by induction on the previous result to prove 
                                                       or
                                                         ex3_2
                                                           T
                                                           T
                                                           λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                           λu2:T.λ:T.pr2 c0 u1 u2
                                                           λ:T
                                                             .λt3:T
                                                               .or3
                                                                 b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                 ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                 ex3_2
                                                                   T
                                                                   T
                                                                   λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                   λy0:T.λz:T.pr0 y0 z
                                                                   λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                         b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                       case or3_intro0 : H11:ex2 T λu2:T.eq T t (THead (Bind Abbr) u2 x1) λu2:T.subst0 i u x0 u2 
                                                          the thesis becomes 
                                                          or
                                                            ex3_2
                                                              T
                                                              T
                                                              λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                              λu2:T.λ:T.pr2 c0 u1 u2
                                                              λ:T
                                                                .λt3:T
                                                                  .or3
                                                                    b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                    ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                    ex3_2
                                                                      T
                                                                      T
                                                                      λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                      λy0:T.λz:T.pr0 y0 z
                                                                      λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                            b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                             we proceed by induction on H11 to prove 
                                                                or
                                                                  ex3_2
                                                                    T
                                                                    T
                                                                    λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                    λu2:T.λ:T.pr2 c0 u1 u2
                                                                    λ:T
                                                                      .λt3:T
                                                                        .or3
                                                                          b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                          ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                          ex3_2
                                                                            T
                                                                            T
                                                                            λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                            λy0:T.λz:T.pr0 y0 z
                                                                            λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                  b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                case ex_intro2 : x2:T H12:eq T t (THead (Bind Abbr) x2 x1) H13:subst0 i u x0 x2 
                                                                   the thesis becomes 
                                                                   or
                                                                     ex3_2
                                                                       T
                                                                       T
                                                                       λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                       λu2:T.λ:T.pr2 c0 u1 u2
                                                                       λ:T
                                                                         .λt3:T
                                                                           .or3
                                                                             b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                             ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                             ex3_2
                                                                               T
                                                                               T
                                                                               λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                               λy0:T.λz:T.pr0 y0 z
                                                                               λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                     b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                      (h1
                                                                         by (pr2_delta . . . . H1 . . H8 . H13)
pr2 c0 u1 x2
                                                                      end of h1
                                                                      (h2
                                                                          assume bB
                                                                          assume u0T
                                                                            by (pr2_free . . . H9)
                                                                            we proved pr2 (CHead c0 (Bind b) u0) t1 x1
                                                                         we proved b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 x1)
                                                                         by (or3_intro0 . . . previous)

                                                                            or3
                                                                              b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 x1)
                                                                              ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 x1
                                                                              ex3_2
                                                                                T
                                                                                T
                                                                                λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                λy0:T.λz:T.pr0 y0 z
                                                                                λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z x1
                                                                      end of h2
                                                                      by (ex3_2_intro . . . . . . . H12 h1 h2)
                                                                      we proved 
                                                                         ex3_2
                                                                           T
                                                                           T
                                                                           λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                           λu2:T.λ:T.pr2 c0 u1 u2
                                                                           λ:T
                                                                             .λt3:T
                                                                               .or3
                                                                                 b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                 ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                 ex3_2
                                                                                   T
                                                                                   T
                                                                                   λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                   λy0:T.λz:T.pr0 y0 z
                                                                                   λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                      by (or_introl . . previous)

                                                                         or
                                                                           ex3_2
                                                                             T
                                                                             T
                                                                             λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                             λu2:T.λ:T.pr2 c0 u1 u2
                                                                             λ:T
                                                                               .λt3:T
                                                                                 .or3
                                                                                   b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                   ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                   ex3_2
                                                                                     T
                                                                                     T
                                                                                     λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                     λy0:T.λz:T.pr0 y0 z
                                                                                     λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                           b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))

                                                                or
                                                                  ex3_2
                                                                    T
                                                                    T
                                                                    λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                    λu2:T.λ:T.pr2 c0 u1 u2
                                                                    λ:T
                                                                      .λt3:T
                                                                        .or3
                                                                          b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                          ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                          ex3_2
                                                                            T
                                                                            T
                                                                            λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                            λy0:T.λz:T.pr0 y0 z
                                                                            λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                  b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                       case or3_intro1 : H11:ex2 T λt3:T.eq T t (THead (Bind Abbr) x0 t3) λt3:T.subst0 (s (Bind Abbr) i) u x1 t3 
                                                          the thesis becomes 
                                                          or
                                                            ex3_2
                                                              T
                                                              T
                                                              λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                              λu2:T.λ:T.pr2 c0 u1 u2
                                                              λ:T
                                                                .λt3:T
                                                                  .or3
                                                                    b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                    ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                    ex3_2
                                                                      T
                                                                      T
                                                                      λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                      λy0:T.λz:T.pr0 y0 z
                                                                      λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                            b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                             we proceed by induction on H11 to prove 
                                                                or
                                                                  ex3_2
                                                                    T
                                                                    T
                                                                    λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                    λu2:T.λ:T.pr2 c0 u1 u2
                                                                    λ:T
                                                                      .λt3:T
                                                                        .or3
                                                                          b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                          ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                          ex3_2
                                                                            T
                                                                            T
                                                                            λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                            λy0:T.λz:T.pr0 y0 z
                                                                            λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                  b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                case ex_intro2 : x2:T H12:eq T t (THead (Bind Abbr) x0 x2) H13:subst0 (s (Bind Abbr) i) u x1 x2 
                                                                   the thesis becomes 
                                                                   or
                                                                     ex3_2
                                                                       T
                                                                       T
                                                                       λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                       λu2:T.λ:T.pr2 c0 u1 u2
                                                                       λ:T
                                                                         .λt3:T
                                                                           .or3
                                                                             b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                             ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                             ex3_2
                                                                               T
                                                                               T
                                                                               λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                               λy0:T.λz:T.pr0 y0 z
                                                                               λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                     b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                      (h1by (pr2_free . . . H8) we proved pr2 c0 u1 x0
                                                                      (h2
                                                                          assume bB
                                                                          assume u0T
                                                                            (h1
                                                                               consider H1
                                                                               we proved getl i c0 (CHead d (Bind Abbr) u)
                                                                               that is equivalent to getl (r (Bind b) i) c0 (CHead d (Bind Abbr) u)
                                                                               by (getl_head . . . . previous .)
getl (S i) (CHead c0 (Bind b) u0) (CHead d (Bind Abbr) u)
                                                                            end of h1
                                                                            (h2
                                                                               consider H13
                                                                               we proved subst0 (s (Bind Abbr) i) u x1 x2
subst0 (S i) u x1 x2
                                                                            end of h2
                                                                            by (pr2_delta . . . . h1 . . H9 . h2)
                                                                            we proved pr2 (CHead c0 (Bind b) u0) t1 x2
                                                                         we proved b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 x2)
                                                                         by (or3_intro0 . . . previous)

                                                                            or3
                                                                              b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 x2)
                                                                              ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 x2
                                                                              ex3_2
                                                                                T
                                                                                T
                                                                                λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                λy0:T.λz:T.pr0 y0 z
                                                                                λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z x2
                                                                      end of h2
                                                                      by (ex3_2_intro . . . . . . . H12 h1 h2)
                                                                      we proved 
                                                                         ex3_2
                                                                           T
                                                                           T
                                                                           λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                           λu2:T.λ:T.pr2 c0 u1 u2
                                                                           λ:T
                                                                             .λt3:T
                                                                               .or3
                                                                                 b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                 ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                 ex3_2
                                                                                   T
                                                                                   T
                                                                                   λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                   λy0:T.λz:T.pr0 y0 z
                                                                                   λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                      by (or_introl . . previous)

                                                                         or
                                                                           ex3_2
                                                                             T
                                                                             T
                                                                             λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                             λu2:T.λ:T.pr2 c0 u1 u2
                                                                             λ:T
                                                                               .λt3:T
                                                                                 .or3
                                                                                   b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                   ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                   ex3_2
                                                                                     T
                                                                                     T
                                                                                     λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                     λy0:T.λz:T.pr0 y0 z
                                                                                     λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                           b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))

                                                                or
                                                                  ex3_2
                                                                    T
                                                                    T
                                                                    λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                    λu2:T.λ:T.pr2 c0 u1 u2
                                                                    λ:T
                                                                      .λt3:T
                                                                        .or3
                                                                          b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                          ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                          ex3_2
                                                                            T
                                                                            T
                                                                            λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                            λy0:T.λz:T.pr0 y0 z
                                                                            λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                  b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                       case or3_intro2 : H11:ex3_2 T T λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3) λu2:T.λ:T.subst0 i u x0 u2 λ:T.λt3:T.subst0 (s (Bind Abbr) i) u x1 t3 
                                                          the thesis becomes 
                                                          or
                                                            ex3_2
                                                              T
                                                              T
                                                              λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                              λu2:T.λ:T.pr2 c0 u1 u2
                                                              λ:T
                                                                .λt3:T
                                                                  .or3
                                                                    b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                    ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                    ex3_2
                                                                      T
                                                                      T
                                                                      λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                      λy0:T.λz:T.pr0 y0 z
                                                                      λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                            b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                             we proceed by induction on H11 to prove 
                                                                or
                                                                  ex3_2
                                                                    T
                                                                    T
                                                                    λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                    λu2:T.λ:T.pr2 c0 u1 u2
                                                                    λ:T
                                                                      .λt3:T
                                                                        .or3
                                                                          b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                          ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                          ex3_2
                                                                            T
                                                                            T
                                                                            λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                            λy0:T.λz:T.pr0 y0 z
                                                                            λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                  b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                case ex3_2_intro : x2:T x3:T H12:eq T t (THead (Bind Abbr) x2 x3) H13:subst0 i u x0 x2 H14:subst0 (s (Bind Abbr) i) u x1 x3 
                                                                   the thesis becomes 
                                                                   or
                                                                     ex3_2
                                                                       T
                                                                       T
                                                                       λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                       λu2:T.λ:T.pr2 c0 u1 u2
                                                                       λ:T
                                                                         .λt3:T
                                                                           .or3
                                                                             b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                             ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                             ex3_2
                                                                               T
                                                                               T
                                                                               λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                               λy0:T.λz:T.pr0 y0 z
                                                                               λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                     b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                      (h1
                                                                         by (pr2_delta . . . . H1 . . H8 . H13)
pr2 c0 u1 x2
                                                                      end of h1
                                                                      (h2
                                                                          assume bB
                                                                          assume u0T
                                                                            (h1
                                                                               consider H1
                                                                               we proved getl i c0 (CHead d (Bind Abbr) u)
                                                                               that is equivalent to getl (r (Bind b) i) c0 (CHead d (Bind Abbr) u)
                                                                               by (getl_head . . . . previous .)
getl (S i) (CHead c0 (Bind b) u0) (CHead d (Bind Abbr) u)
                                                                            end of h1
                                                                            (h2
                                                                               consider H14
                                                                               we proved subst0 (s (Bind Abbr) i) u x1 x3
subst0 (S i) u x1 x3
                                                                            end of h2
                                                                            by (pr2_delta . . . . h1 . . H9 . h2)
                                                                            we proved pr2 (CHead c0 (Bind b) u0) t1 x3
                                                                         we proved b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 x3)
                                                                         by (or3_intro0 . . . previous)

                                                                            or3
                                                                              b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 x3)
                                                                              ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 x3
                                                                              ex3_2
                                                                                T
                                                                                T
                                                                                λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                λy0:T.λz:T.pr0 y0 z
                                                                                λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z x3
                                                                      end of h2
                                                                      by (ex3_2_intro . . . . . . . H12 h1 h2)
                                                                      we proved 
                                                                         ex3_2
                                                                           T
                                                                           T
                                                                           λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                           λu2:T.λ:T.pr2 c0 u1 u2
                                                                           λ:T
                                                                             .λt3:T
                                                                               .or3
                                                                                 b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                 ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                 ex3_2
                                                                                   T
                                                                                   T
                                                                                   λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                   λy0:T.λz:T.pr0 y0 z
                                                                                   λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                      by (or_introl . . previous)

                                                                         or
                                                                           ex3_2
                                                                             T
                                                                             T
                                                                             λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                             λu2:T.λ:T.pr2 c0 u1 u2
                                                                             λ:T
                                                                               .λt3:T
                                                                                 .or3
                                                                                   b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                   ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                   ex3_2
                                                                                     T
                                                                                     T
                                                                                     λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                     λy0:T.λz:T.pr0 y0 z
                                                                                     λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                           b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))

                                                                or
                                                                  ex3_2
                                                                    T
                                                                    T
                                                                    λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                    λu2:T.λ:T.pr2 c0 u1 u2
                                                                    λ:T
                                                                      .λt3:T
                                                                        .or3
                                                                          b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                          ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                          ex3_2
                                                                            T
                                                                            T
                                                                            λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                            λy0:T.λz:T.pr0 y0 z
                                                                            λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                  b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))

                                                       or
                                                         ex3_2
                                                           T
                                                           T
                                                           λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                           λu2:T.λ:T.pr2 c0 u1 u2
                                                           λ:T
                                                             .λt3:T
                                                               .or3
                                                                 b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                 ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                 ex3_2
                                                                   T
                                                                   T
                                                                   λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                   λy0:T.λz:T.pr0 y0 z
                                                                   λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                         b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                              case or_intror : H_x0:ex2 T λy0:T.pr0 t1 y0 λy0:T.subst0 O x0 y0 x1 
                                                 the thesis becomes 
                                                 or
                                                   ex3_2
                                                     T
                                                     T
                                                     λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                     λu2:T.λ:T.pr2 c0 u1 u2
                                                     λ:T
                                                       .λt3:T
                                                         .or3
                                                           b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                           ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                           ex3_2
                                                             T
                                                             T
                                                             λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                             λy0:T.λz:T.pr0 y0 z
                                                             λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                   b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                    we proceed by induction on H_x0 to prove 
                                                       or
                                                         ex3_2
                                                           T
                                                           T
                                                           λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                           λu2:T.λ:T.pr2 c0 u1 u2
                                                           λ:T
                                                             .λt3:T
                                                               .or3
                                                                 b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                 ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                 ex3_2
                                                                   T
                                                                   T
                                                                   λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                   λy0:T.λz:T.pr0 y0 z
                                                                   λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                         b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                       case ex_intro2 : x2:T H9:pr0 t1 x2 H10:subst0 O x0 x2 x1 
                                                          the thesis becomes 
                                                          or
                                                            ex3_2
                                                              T
                                                              T
                                                              λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                              λu2:T.λ:T.pr2 c0 u1 u2
                                                              λ:T
                                                                .λt3:T
                                                                  .or3
                                                                    b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                    ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                    ex3_2
                                                                      T
                                                                      T
                                                                      λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                      λy0:T.λz:T.pr0 y0 z
                                                                      λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                            b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                             (H11
                                                                we proceed by induction on H7 to prove subst0 i u (THead (Bind Abbr) x0 x1) t
                                                                   case refl_equal : 
                                                                      the thesis becomes the hypothesis H3
subst0 i u (THead (Bind Abbr) x0 x1) t
                                                             end of H11
                                                             by (subst0_gen_head . . . . . . H11)
                                                             we proved 
                                                                or3
                                                                  ex2 T λu2:T.eq T t (THead (Bind Abbr) u2 x1) λu2:T.subst0 i u x0 u2
                                                                  ex2 T λt2:T.eq T t (THead (Bind Abbr) x0 t2) λt2:T.subst0 (s (Bind Abbr) i) u x1 t2
                                                                  ex3_2
                                                                    T
                                                                    T
                                                                    λu2:T.λt2:T.eq T t (THead (Bind Abbr) u2 t2)
                                                                    λu2:T.λ:T.subst0 i u x0 u2
                                                                    λ:T.λt2:T.subst0 (s (Bind Abbr) i) u x1 t2
                                                             we proceed by induction on the previous result to prove 
                                                                or
                                                                  ex3_2
                                                                    T
                                                                    T
                                                                    λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                    λu2:T.λ:T.pr2 c0 u1 u2
                                                                    λ:T
                                                                      .λt3:T
                                                                        .or3
                                                                          b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                          ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                          ex3_2
                                                                            T
                                                                            T
                                                                            λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                            λy0:T.λz:T.pr0 y0 z
                                                                            λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                  b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                case or3_intro0 : H12:ex2 T λu2:T.eq T t (THead (Bind Abbr) u2 x1) λu2:T.subst0 i u x0 u2 
                                                                   the thesis becomes 
                                                                   or
                                                                     ex3_2
                                                                       T
                                                                       T
                                                                       λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                       λu2:T.λ:T.pr2 c0 u1 u2
                                                                       λ:T
                                                                         .λt3:T
                                                                           .or3
                                                                             b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                             ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                             ex3_2
                                                                               T
                                                                               T
                                                                               λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                               λy0:T.λz:T.pr0 y0 z
                                                                               λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                     b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                      we proceed by induction on H12 to prove 
                                                                         or
                                                                           ex3_2
                                                                             T
                                                                             T
                                                                             λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                             λu2:T.λ:T.pr2 c0 u1 u2
                                                                             λ:T
                                                                               .λt3:T
                                                                                 .or3
                                                                                   b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                   ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                   ex3_2
                                                                                     T
                                                                                     T
                                                                                     λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                     λy0:T.λz:T.pr0 y0 z
                                                                                     λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                           b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                         case ex_intro2 : x3:T H13:eq T t (THead (Bind Abbr) x3 x1) H14:subst0 i u x0 x3 
                                                                            the thesis becomes 
                                                                            or
                                                                              ex3_2
                                                                                T
                                                                                T
                                                                                λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                                λu2:T.λ:T.pr2 c0 u1 u2
                                                                                λ:T
                                                                                  .λt3:T
                                                                                    .or3
                                                                                      b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                      ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                      ex3_2
                                                                                        T
                                                                                        T
                                                                                        λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                        λy0:T.λz:T.pr0 y0 z
                                                                                        λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                              b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                               by (pr0_subst0_back . . . . H10 . H8)
                                                                               we proved ex2 T λt:T.subst0 O u1 x2 t λt:T.pr0 t x1
                                                                               we proceed by induction on the previous result to prove 
                                                                                  or
                                                                                    ex3_2
                                                                                      T
                                                                                      T
                                                                                      λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                                      λu2:T.λ:T.pr2 c0 u1 u2
                                                                                      λ:T
                                                                                        .λt3:T
                                                                                          .or3
                                                                                            b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                            ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                            ex3_2
                                                                                              T
                                                                                              T
                                                                                              λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                              λy0:T.λz:T.pr0 y0 z
                                                                                              λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                                    b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                                  case ex_intro2 : x4:T :subst0 O u1 x2 x4 :pr0 x4 x1 
                                                                                     the thesis becomes 
                                                                                     or
                                                                                       ex3_2
                                                                                         T
                                                                                         T
                                                                                         λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                                         λu2:T.λ:T.pr2 c0 u1 u2
                                                                                         λ:T
                                                                                           .λt3:T
                                                                                             .or3
                                                                                               b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                               ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                               ex3_2
                                                                                                 T
                                                                                                 T
                                                                                                 λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                                 λy0:T.λz:T.pr0 y0 z
                                                                                                 λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                                       b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                                        (h1
                                                                                           by (pr2_delta . . . . H1 . . H8 . H14)
pr2 c0 u1 x3
                                                                                        end of h1
                                                                                        (h2
                                                                                           by (getl_refl . . .)
                                                                                           we proved getl O (CHead c0 (Bind Abbr) x0) (CHead c0 (Bind Abbr) x0)
                                                                                           by (pr2_delta . . . . previous . . H9 . H10)
                                                                                           we proved pr2 (CHead c0 (Bind Abbr) x0) t1 x1
                                                                                           by (ex_intro2 . . . . H8 previous)
                                                                                           we proved ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 x1
                                                                                           by (or3_intro1 . . . previous)

                                                                                              or3
                                                                                                b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 x1)
                                                                                                ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 x1
                                                                                                ex3_2
                                                                                                  T
                                                                                                  T
                                                                                                  λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                                  λy0:T.λz:T.pr0 y0 z
                                                                                                  λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z x1
                                                                                        end of h2
                                                                                        by (ex3_2_intro . . . . . . . H13 h1 h2)
                                                                                        we proved 
                                                                                           ex3_2
                                                                                             T
                                                                                             T
                                                                                             λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                                             λu2:T.λ:T.pr2 c0 u1 u2
                                                                                             λ:T
                                                                                               .λt3:T
                                                                                                 .or3
                                                                                                   b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                                   ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                                   ex3_2
                                                                                                     T
                                                                                                     T
                                                                                                     λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                                     λy0:T.λz:T.pr0 y0 z
                                                                                                     λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                                        by (or_introl . . previous)

                                                                                           or
                                                                                             ex3_2
                                                                                               T
                                                                                               T
                                                                                               λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                                               λu2:T.λ:T.pr2 c0 u1 u2
                                                                                               λ:T
                                                                                                 .λt3:T
                                                                                                   .or3
                                                                                                     b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                                     ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                                     ex3_2
                                                                                                       T
                                                                                                       T
                                                                                                       λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                                       λy0:T.λz:T.pr0 y0 z
                                                                                                       λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                                             b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))

                                                                                  or
                                                                                    ex3_2
                                                                                      T
                                                                                      T
                                                                                      λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                                      λu2:T.λ:T.pr2 c0 u1 u2
                                                                                      λ:T
                                                                                        .λt3:T
                                                                                          .or3
                                                                                            b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                            ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                            ex3_2
                                                                                              T
                                                                                              T
                                                                                              λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                              λy0:T.λz:T.pr0 y0 z
                                                                                              λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                                    b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))

                                                                         or
                                                                           ex3_2
                                                                             T
                                                                             T
                                                                             λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                             λu2:T.λ:T.pr2 c0 u1 u2
                                                                             λ:T
                                                                               .λt3:T
                                                                                 .or3
                                                                                   b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                   ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                   ex3_2
                                                                                     T
                                                                                     T
                                                                                     λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                     λy0:T.λz:T.pr0 y0 z
                                                                                     λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                           b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                case or3_intro1 : H12:ex2 T λt3:T.eq T t (THead (Bind Abbr) x0 t3) λt3:T.subst0 (s (Bind Abbr) i) u x1 t3 
                                                                   the thesis becomes 
                                                                   or
                                                                     ex3_2
                                                                       T
                                                                       T
                                                                       λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                       λu2:T.λ:T.pr2 c0 u1 u2
                                                                       λ:T
                                                                         .λt3:T
                                                                           .or3
                                                                             b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                             ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                             ex3_2
                                                                               T
                                                                               T
                                                                               λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                               λy0:T.λz:T.pr0 y0 z
                                                                               λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                     b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                      we proceed by induction on H12 to prove 
                                                                         or
                                                                           ex3_2
                                                                             T
                                                                             T
                                                                             λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                             λu2:T.λ:T.pr2 c0 u1 u2
                                                                             λ:T
                                                                               .λt3:T
                                                                                 .or3
                                                                                   b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                   ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                   ex3_2
                                                                                     T
                                                                                     T
                                                                                     λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                     λy0:T.λz:T.pr0 y0 z
                                                                                     λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                           b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                         case ex_intro2 : x3:T H13:eq T t (THead (Bind Abbr) x0 x3) H14:subst0 (s (Bind Abbr) i) u x1 x3 
                                                                            the thesis becomes 
                                                                            or
                                                                              ex3_2
                                                                                T
                                                                                T
                                                                                λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                                λu2:T.λ:T.pr2 c0 u1 u2
                                                                                λ:T
                                                                                  .λt3:T
                                                                                    .or3
                                                                                      b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                      ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                      ex3_2
                                                                                        T
                                                                                        T
                                                                                        λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                        λy0:T.λz:T.pr0 y0 z
                                                                                        λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                              b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                               by (pr0_subst0_back . . . . H10 . H8)
                                                                               we proved ex2 T λt:T.subst0 O u1 x2 t λt:T.pr0 t x1
                                                                               we proceed by induction on the previous result to prove 
                                                                                  or
                                                                                    ex3_2
                                                                                      T
                                                                                      T
                                                                                      λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                                      λu2:T.λ:T.pr2 c0 u1 u2
                                                                                      λ:T
                                                                                        .λt3:T
                                                                                          .or3
                                                                                            b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                            ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                            ex3_2
                                                                                              T
                                                                                              T
                                                                                              λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                              λy0:T.λz:T.pr0 y0 z
                                                                                              λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                                    b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                                  case ex_intro2 : x4:T H15:subst0 O u1 x2 x4 H16:pr0 x4 x1 
                                                                                     the thesis becomes 
                                                                                     or
                                                                                       ex3_2
                                                                                         T
                                                                                         T
                                                                                         λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                                         λu2:T.λ:T.pr2 c0 u1 u2
                                                                                         λ:T
                                                                                           .λt3:T
                                                                                             .or3
                                                                                               b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                               ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                               ex3_2
                                                                                                 T
                                                                                                 T
                                                                                                 λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                                 λy0:T.λz:T.pr0 y0 z
                                                                                                 λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                                       b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                                        (h1by (pr2_free . . . H8) we proved pr2 c0 u1 x0
                                                                                        (h2
                                                                                           (h1
                                                                                              by (getl_refl . . .)
                                                                                              we proved getl O (CHead c0 (Bind Abbr) u1) (CHead c0 (Bind Abbr) u1)
                                                                                              by (pr2_delta . . . . previous . . H9 . H15)
pr2 (CHead c0 (Bind Abbr) u1) t1 x4
                                                                                           end of h1
                                                                                           (h2
                                                                                              (h1
                                                                                                 consider H1
                                                                                                 we proved getl i c0 (CHead d (Bind Abbr) u)
                                                                                                 that is equivalent to getl (r (Bind Abbr) i) c0 (CHead d (Bind Abbr) u)
                                                                                                 by (getl_head . . . . previous .)
getl (S i) (CHead c0 (Bind Abbr) u1) (CHead d (Bind Abbr) u)
                                                                                              end of h1
                                                                                              (h2by (pr0_refl .) we proved pr0 x1 x1
                                                                                              (h3
                                                                                                 consider H14
                                                                                                 we proved subst0 (s (Bind Abbr) i) u x1 x3
subst0 (S i) u x1 x3
                                                                                              end of h3
                                                                                              by (pr2_delta . . . . h1 . . h2 . h3)
pr2 (CHead c0 (Bind Abbr) u1) x1 x3
                                                                                           end of h2
                                                                                           by (ex3_2_intro . . . . . . . h1 H16 h2)
                                                                                           we proved 
                                                                                              ex3_2
                                                                                                T
                                                                                                T
                                                                                                λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                                λy0:T.λz:T.pr0 y0 z
                                                                                                λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z x3
                                                                                           by (or3_intro2 . . . previous)

                                                                                              or3
                                                                                                b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 x3)
                                                                                                ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 x3
                                                                                                ex3_2
                                                                                                  T
                                                                                                  T
                                                                                                  λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                                  λy0:T.λz:T.pr0 y0 z
                                                                                                  λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z x3
                                                                                        end of h2
                                                                                        by (ex3_2_intro . . . . . . . H13 h1 h2)
                                                                                        we proved 
                                                                                           ex3_2
                                                                                             T
                                                                                             T
                                                                                             λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                                             λu2:T.λ:T.pr2 c0 u1 u2
                                                                                             λ:T
                                                                                               .λt3:T
                                                                                                 .or3
                                                                                                   b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                                   ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                                   ex3_2
                                                                                                     T
                                                                                                     T
                                                                                                     λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                                     λy0:T.λz:T.pr0 y0 z
                                                                                                     λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                                        by (or_introl . . previous)

                                                                                           or
                                                                                             ex3_2
                                                                                               T
                                                                                               T
                                                                                               λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                                               λu2:T.λ:T.pr2 c0 u1 u2
                                                                                               λ:T
                                                                                                 .λt3:T
                                                                                                   .or3
                                                                                                     b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                                     ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                                     ex3_2
                                                                                                       T
                                                                                                       T
                                                                                                       λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                                       λy0:T.λz:T.pr0 y0 z
                                                                                                       λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                                             b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))

                                                                                  or
                                                                                    ex3_2
                                                                                      T
                                                                                      T
                                                                                      λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                                      λu2:T.λ:T.pr2 c0 u1 u2
                                                                                      λ:T
                                                                                        .λt3:T
                                                                                          .or3
                                                                                            b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                            ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                            ex3_2
                                                                                              T
                                                                                              T
                                                                                              λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                              λy0:T.λz:T.pr0 y0 z
                                                                                              λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                                    b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))

                                                                         or
                                                                           ex3_2
                                                                             T
                                                                             T
                                                                             λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                             λu2:T.λ:T.pr2 c0 u1 u2
                                                                             λ:T
                                                                               .λt3:T
                                                                                 .or3
                                                                                   b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                   ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                   ex3_2
                                                                                     T
                                                                                     T
                                                                                     λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                     λy0:T.λz:T.pr0 y0 z
                                                                                     λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                           b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                case or3_intro2 : H12:ex3_2 T T λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3) λu2:T.λ:T.subst0 i u x0 u2 λ:T.λt3:T.subst0 (s (Bind Abbr) i) u x1 t3 
                                                                   the thesis becomes 
                                                                   or
                                                                     ex3_2
                                                                       T
                                                                       T
                                                                       λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                       λu2:T.λ:T.pr2 c0 u1 u2
                                                                       λ:T
                                                                         .λt3:T
                                                                           .or3
                                                                             b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                             ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                             ex3_2
                                                                               T
                                                                               T
                                                                               λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                               λy0:T.λz:T.pr0 y0 z
                                                                               λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                     b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                      we proceed by induction on H12 to prove 
                                                                         or
                                                                           ex3_2
                                                                             T
                                                                             T
                                                                             λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                             λu2:T.λ:T.pr2 c0 u1 u2
                                                                             λ:T
                                                                               .λt3:T
                                                                                 .or3
                                                                                   b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                   ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                   ex3_2
                                                                                     T
                                                                                     T
                                                                                     λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                     λy0:T.λz:T.pr0 y0 z
                                                                                     λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                           b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                         case ex3_2_intro : x3:T x4:T H13:eq T t (THead (Bind Abbr) x3 x4) H14:subst0 i u x0 x3 H15:subst0 (s (Bind Abbr) i) u x1 x4 
                                                                            the thesis becomes 
                                                                            or
                                                                              ex3_2
                                                                                T
                                                                                T
                                                                                λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                                λu2:T.λ:T.pr2 c0 u1 u2
                                                                                λ:T
                                                                                  .λt3:T
                                                                                    .or3
                                                                                      b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                      ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                      ex3_2
                                                                                        T
                                                                                        T
                                                                                        λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                        λy0:T.λz:T.pr0 y0 z
                                                                                        λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                              b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                               by (pr0_subst0_back . . . . H10 . H8)
                                                                               we proved ex2 T λt:T.subst0 O u1 x2 t λt:T.pr0 t x1
                                                                               we proceed by induction on the previous result to prove 
                                                                                  or
                                                                                    ex3_2
                                                                                      T
                                                                                      T
                                                                                      λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                                      λu2:T.λ:T.pr2 c0 u1 u2
                                                                                      λ:T
                                                                                        .λt3:T
                                                                                          .or3
                                                                                            b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                            ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                            ex3_2
                                                                                              T
                                                                                              T
                                                                                              λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                              λy0:T.λz:T.pr0 y0 z
                                                                                              λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                                    b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                                  case ex_intro2 : x5:T H16:subst0 O u1 x2 x5 H17:pr0 x5 x1 
                                                                                     the thesis becomes 
                                                                                     or
                                                                                       ex3_2
                                                                                         T
                                                                                         T
                                                                                         λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                                         λu2:T.λ:T.pr2 c0 u1 u2
                                                                                         λ:T
                                                                                           .λt3:T
                                                                                             .or3
                                                                                               b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                               ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                               ex3_2
                                                                                                 T
                                                                                                 T
                                                                                                 λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                                 λy0:T.λz:T.pr0 y0 z
                                                                                                 λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                                       b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                                                                        (h1
                                                                                           by (pr2_delta . . . . H1 . . H8 . H14)
pr2 c0 u1 x3
                                                                                        end of h1
                                                                                        (h2
                                                                                           (h1
                                                                                              by (getl_refl . . .)
                                                                                              we proved getl O (CHead c0 (Bind Abbr) u1) (CHead c0 (Bind Abbr) u1)
                                                                                              by (pr2_delta . . . . previous . . H9 . H16)
pr2 (CHead c0 (Bind Abbr) u1) t1 x5
                                                                                           end of h1
                                                                                           (h2
                                                                                              (h1
                                                                                                 consider H1
                                                                                                 we proved getl i c0 (CHead d (Bind Abbr) u)
                                                                                                 that is equivalent to getl (r (Bind Abbr) i) c0 (CHead d (Bind Abbr) u)
                                                                                                 by (getl_head . . . . previous .)
getl (S i) (CHead c0 (Bind Abbr) u1) (CHead d (Bind Abbr) u)
                                                                                              end of h1
                                                                                              (h2by (pr0_refl .) we proved pr0 x1 x1
                                                                                              (h3
                                                                                                 consider H15
                                                                                                 we proved subst0 (s (Bind Abbr) i) u x1 x4
subst0 (S i) u x1 x4
                                                                                              end of h3
                                                                                              by (pr2_delta . . . . h1 . . h2 . h3)
pr2 (CHead c0 (Bind Abbr) u1) x1 x4
                                                                                           end of h2
                                                                                           by (ex3_2_intro . . . . . . . h1 H17 h2)
                                                                                           we proved 
                                                                                              ex3_2
                                                                                                T
                                                                                                T
                                                                                                λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                                λy0:T.λz:T.pr0 y0 z
                                                                                                λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z x4
                                                                                           by (or3_intro2 . . . previous)

                                                                                              or3
                                                                                                b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 x4)
                                                                                                ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 x4
                                                                                                ex3_2
                                                                                                  T
                                                                                                  T
                                                                                                  λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                                  λy0:T.λz:T.pr0 y0 z
                                                                                                  λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z x4
                                                                                        end of h2
                                                                                        by (ex3_2_intro . . . . . . . H13 h1 h2)
                                                                                        we proved 
                                                                                           ex3_2
                                                                                             T
                                                                                             T
                                                                                             λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                                             λu2:T.λ:T.pr2 c0 u1 u2
                                                                                             λ:T
                                                                                               .λt3:T
                                                                                                 .or3
                                                                                                   b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                                   ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                                   ex3_2
                                                                                                     T
                                                                                                     T
                                                                                                     λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                                     λy0:T.λz:T.pr0 y0 z
                                                                                                     λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                                        by (or_introl . . previous)

                                                                                           or
                                                                                             ex3_2
                                                                                               T
                                                                                               T
                                                                                               λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                                               λu2:T.λ:T.pr2 c0 u1 u2
                                                                                               λ:T
                                                                                                 .λt3:T
                                                                                                   .or3
                                                                                                     b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                                     ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                                     ex3_2
                                                                                                       T
                                                                                                       T
                                                                                                       λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                                       λy0:T.λz:T.pr0 y0 z
                                                                                                       λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                                             b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))

                                                                                  or
                                                                                    ex3_2
                                                                                      T
                                                                                      T
                                                                                      λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                                      λu2:T.λ:T.pr2 c0 u1 u2
                                                                                      λ:T
                                                                                        .λt3:T
                                                                                          .or3
                                                                                            b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                            ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                            ex3_2
                                                                                              T
                                                                                              T
                                                                                              λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                              λy0:T.λz:T.pr0 y0 z
                                                                                              λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                                    b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))

                                                                         or
                                                                           ex3_2
                                                                             T
                                                                             T
                                                                             λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                             λu2:T.λ:T.pr2 c0 u1 u2
                                                                             λ:T
                                                                               .λt3:T
                                                                                 .or3
                                                                                   b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                                   ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                                   ex3_2
                                                                                     T
                                                                                     T
                                                                                     λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                                     λy0:T.λz:T.pr0 y0 z
                                                                                     λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                           b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))

                                                                or
                                                                  ex3_2
                                                                    T
                                                                    T
                                                                    λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                                    λu2:T.λ:T.pr2 c0 u1 u2
                                                                    λ:T
                                                                      .λt3:T
                                                                        .or3
                                                                          b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                          ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                          ex3_2
                                                                            T
                                                                            T
                                                                            λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                            λy0:T.λz:T.pr0 y0 z
                                                                            λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                                  b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))

                                                       or
                                                         ex3_2
                                                           T
                                                           T
                                                           λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                           λu2:T.λ:T.pr2 c0 u1 u2
                                                           λ:T
                                                             .λt3:T
                                                               .or3
                                                                 b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                                 ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                                 ex3_2
                                                                   T
                                                                   T
                                                                   λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                                   λy0:T.λz:T.pr0 y0 z
                                                                   λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                         b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))

                                              or
                                                ex3_2
                                                  T
                                                  T
                                                  λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                                  λu2:T.λ:T.pr2 c0 u1 u2
                                                  λ:T
                                                    .λt3:T
                                                      .or3
                                                        b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                                        ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                                        ex3_2
                                                          T
                                                          T
                                                          λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                          λy0:T.λz:T.pr0 y0 z
                                                          λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                                b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))

                                     or
                                       ex3_2
                                         T
                                         T
                                         λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                         λu2:T.λ:T.pr2 c0 u1 u2
                                         λ:T
                                           .λt3:T
                                             .or3
                                               b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                               ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                               ex3_2
                                                 T
                                                 T
                                                 λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                 λy0:T.λz:T.pr0 y0 z
                                                 λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                       b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                            case or_intror : H6:pr0 t1 (lift (S OO t2) 
                               the thesis becomes 
                               or
                                 ex3_2
                                   T
                                   T
                                   λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                   λu2:T.λ:T.pr2 c0 u1 u2
                                   λ:T
                                     .λt3:T
                                       .or3
                                         b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                         ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                         ex3_2
                                           T
                                           T
                                           λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                           λy0:T.λz:T.pr0 y0 z
                                           λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                 b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                   assume bB
                                   assume u0T
                                     (h1
                                        consider H1
                                        we proved getl i c0 (CHead d (Bind Abbr) u)
                                        that is equivalent to getl (r (Bind b) i) c0 (CHead d (Bind Abbr) u)
                                        by (getl_head . . . . previous .)
getl (S i) (CHead c0 (Bind b) u0) (CHead d (Bind Abbr) u)
                                     end of h1
                                     (h2
                                        by (le_O_n .)
                                        we proved le O i
                                        by (subst0_lift_ge_S . . . . H3 . previous)
subst0 (S i) u (lift (S OO t2) (lift (S OO t)
                                     end of h2
                                     by (pr2_delta . . . . h1 . . H6 . h2)
                                     we proved pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t)
                                  we proved b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                                  by (or_intror . . previous)

                                     or
                                       ex3_2
                                         T
                                         T
                                         λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                         λu2:T.λ:T.pr2 c0 u1 u2
                                         λ:T
                                           .λt3:T
                                             .or3
                                               b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                               ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                               ex3_2
                                                 T
                                                 T
                                                 λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                                 λy0:T.λz:T.pr0 y0 z
                                                 λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                                       b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
                         we proved 
                            or
                              ex3_2
                                T
                                T
                                λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                                λu2:T.λ:T.pr2 c0 u1 u2
                                λ:T
                                  .λt3:T
                                    .or3
                                      b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                      ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                      ex3_2
                                        T
                                        T
                                        λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                        λy0:T.λz:T.pr0 y0 z
                                        λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                              b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))

                         H4:eq T t0 (THead (Bind Abbr) u1 t1)
                           .or
                             ex3_2
                               T
                               T
                               λu2:T.λt3:T.eq T t (THead (Bind Abbr) u2 t3)
                               λu2:T.λ:T.pr2 c0 u1 u2
                               λ:T
                                 .λt3:T
                                   .or3
                                     b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 t3)
                                     ex2 T λu0:T.pr0 u1 u0 λu0:T.pr2 (CHead c0 (Bind Abbr) u0) t1 t3
                                     ex3_2
                                       T
                                       T
                                       λy0:T.λ:T.pr2 (CHead c0 (Bind Abbr) u1) t1 y0
                                       λy0:T.λz:T.pr0 y0 z
                                       λ:T.λz:T.pr2 (CHead c0 (Bind Abbr) u1) z t3
                             b:B.u0:T.(pr2 (CHead c0 (Bind b) u0) t1 (lift (S OO t))
             we proved 
                eq T y (THead (Bind Abbr) u1 t1)
                  (or
                       ex3_2
                         T
                         T
                         λu2:T.λt2:T.eq T x (THead (Bind Abbr) u2 t2)
                         λu2:T.λ:T.pr2 c u1 u2
                         λ:T
                           .λt2:T
                             .or3
                               b:B.u:T.(pr2 (CHead c (Bind b) u) t1 t2)
                               ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c (Bind Abbr) u) t1 t2
                               ex3_2
                                 T
                                 T
                                 λy0:T.λ:T.pr2 (CHead c (Bind Abbr) u1) t1 y0
                                 λy0:T.λz:T.pr0 y0 z
                                 λ:T.λz:T.pr2 (CHead c (Bind Abbr) u1) z t2
                       b:B.u:T.(pr2 (CHead c (Bind b) u) t1 (lift (S OO x)))
          we proved 
             y:T
               .pr2 c y x
                 (eq T y (THead (Bind Abbr) u1 t1)
                      (or
                           ex3_2
                             T
                             T
                             λu2:T.λt2:T.eq T x (THead (Bind Abbr) u2 t2)
                             λu2:T.λ:T.pr2 c u1 u2
                             λ:T
                               .λt2:T
                                 .or3
                                   b:B.u:T.(pr2 (CHead c (Bind b) u) t1 t2)
                                   ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c (Bind Abbr) u) t1 t2
                                   ex3_2
                                     T
                                     T
                                     λy0:T.λ:T.pr2 (CHead c (Bind Abbr) u1) t1 y0
                                     λy0:T.λz:T.pr0 y0 z
                                     λ:T.λz:T.pr2 (CHead c (Bind Abbr) u1) z t2
                           b:B.u:T.(pr2 (CHead c (Bind b) u) t1 (lift (S OO x))))
          by (insert_eq . . . . previous H)
          we proved 
             or
               ex3_2
                 T
                 T
                 λu2:T.λt2:T.eq T x (THead (Bind Abbr) u2 t2)
                 λu2:T.λ:T.pr2 c u1 u2
                 λ:T
                   .λt2:T
                     .or3
                       b:B.u:T.(pr2 (CHead c (Bind b) u) t1 t2)
                       ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c (Bind Abbr) u) t1 t2
                       ex3_2
                         T
                         T
                         λy:T.λ:T.pr2 (CHead c (Bind Abbr) u1) t1 y
                         λy:T.λz:T.pr0 y z
                         λ:T.λz:T.pr2 (CHead c (Bind Abbr) u1) z t2
               b:B.u:T.(pr2 (CHead c (Bind b) u) t1 (lift (S OO x))
       we proved 
          c:C
            .u1:T
              .t1:T
                .x:T
                  .pr2 c (THead (Bind Abbr) u1 t1) x
                    (or
                         ex3_2
                           T
                           T
                           λu2:T.λt2:T.eq T x (THead (Bind Abbr) u2 t2)
                           λu2:T.λ:T.pr2 c u1 u2
                           λ:T
                             .λt2:T
                               .or3
                                 b:B.u:T.(pr2 (CHead c (Bind b) u) t1 t2)
                                 ex2 T λu:T.pr0 u1 u λu:T.pr2 (CHead c (Bind Abbr) u) t1 t2
                                 ex3_2
                                   T
                                   T
                                   λy:T.λ:T.pr2 (CHead c (Bind Abbr) u1) t1 y
                                   λy:T.λz:T.pr0 y z
                                   λ:T.λz:T.pr2 (CHead c (Bind Abbr) u1) z t2
                         b:B.u:T.(pr2 (CHead c (Bind b) u) t1 (lift (S OO x)))