DEFINITION sn3_appl_appl()
TYPE =
       v1:T
         .t1:T
           .let u1 := THead (Flat Appl) v1 t1
           in c:C
                  .sn3 c u1
                    v2:T
                         .sn3 c v2
                           (u2:T.(pr3 c u1 u2)((iso u1 u2)P:Prop.P)(sn3 c (THead (Flat Appl) v2 u2))
                                sn3 c (THead (Flat Appl) v2 u1))
BODY =
        assume v1T
        assume t1T
          we must prove 
                let u1 := THead (Flat Appl) v1 t1
                in c:C
                       .sn3 c u1
                         v2:T
                              .sn3 c v2
                                (u2:T.(pr3 c u1 u2)((iso u1 u2)P:Prop.P)(sn3 c (THead (Flat Appl) v2 u2))
                                     sn3 c (THead (Flat Appl) v2 u1))
          or equivalently 
                c:C
                  .sn3 c (THead (Flat Appl) v1 t1)
                    v2:T
                         .sn3 c v2
                           (u2:T
                                  .pr3 c (THead (Flat Appl) v1 t1) u2
                                    ((iso (THead (Flat Appl) v1 t1) u2)P:Prop.P
                                         sn3 c (THead (Flat Appl) v2 u2))
                                sn3 c (THead (Flat Appl) v2 (THead (Flat Appl) v1 t1)))
           assume cC
           suppose Hsn3 c (THead (Flat Appl) v1 t1)
              assume yT
              suppose H0sn3 c y
                we proceed by induction on H0 to prove 
                   x:T
                     .x0:T
                       .eq T y (THead (Flat Appl) x x0)
                         v2:T
                              .sn3 c v2
                                (u2:T
                                       .pr3 c y u2
                                         ((iso y u2)P:Prop.P)(sn3 c (THead (Flat Appl) v2 u2))
                                     sn3 c (THead (Flat Appl) v2 y))
                   case sn3_sing : t2:T H1:t3:T.((eq T t2 t3)P:Prop.P)(pr3 c t2 t3)(sn3 c t3) 
                      the thesis becomes 
                      x:T
                        .x0:T
                          .H3:eq T t2 (THead (Flat Appl) x x0)
                            .v2:T
                              .H4:sn3 c v2
                                .u2:T.(pr3 c t2 u2)((iso t2 u2)P:Prop.P)(sn3 c (THead (Flat Appl) v2 u2))
                                  sn3 c (THead (Flat Appl) v2 t2)
                      (H2) by induction hypothesis we know 
                         t3:T
                           .(eq T t2 t3)P:Prop.P
                             (pr3 c t2 t3
                                  x:T
                                       .x0:T
                                         .eq T t3 (THead (Flat Appl) x x0)
                                           v2:T
                                                .sn3 c v2
                                                  (u2:T.(pr3 c t3 u2)((iso t3 u2)P:Prop.P)(sn3 c (THead (Flat Appl) v2 u2))
                                                       sn3 c (THead (Flat Appl) v2 t3)))
                          assume xT
                          assume x0T
                          suppose H3eq T t2 (THead (Flat Appl) x x0)
                          assume v2T
                          suppose H4sn3 c v2
                            we proceed by induction on H4 to prove 
                               u2:T.(pr3 c t2 u2)((iso t2 u2)P:Prop.P)(sn3 c (THead (Flat Appl) v2 u2))
                                 sn3 c (THead (Flat Appl) v2 t2)
                               case sn3_sing : t0:T H5:t3:T.((eq T t0 t3)P:Prop.P)(pr3 c t0 t3)(sn3 c t3) 
                                  the thesis becomes 
                                  H7:u2:T.(pr3 c t2 u2)((iso t2 u2)P:Prop.P)(sn3 c (THead (Flat Appl) t0 u2))
                                    .sn3 c (THead (Flat Appl) t0 t2)
                                  (H6) by induction hypothesis we know 
                                     t3:T
                                       .(eq T t0 t3)P:Prop.P
                                         (pr3 c t0 t3
                                              (u2:T.(pr3 c t2 u2)((iso t2 u2)P:Prop.P)(sn3 c (THead (Flat Appl) t3 u2))
                                                   sn3 c (THead (Flat Appl) t3 t2)))
                                     suppose H7
                                        u2:T.(pr3 c t2 u2)((iso t2 u2)P:Prop.P)(sn3 c (THead (Flat Appl) t0 u2))
                                        (H8
                                           we proceed by induction on H3 to prove 
                                              u2:T
                                                .pr3 c (THead (Flat Appl) x x0) u2
                                                  ((iso (THead (Flat Appl) x x0) u2)P:Prop.P
                                                       sn3 c (THead (Flat Appl) t0 u2))
                                              case refl_equal : 
                                                 the thesis becomes the hypothesis H7

                                              u2:T
                                                .pr3 c (THead (Flat Appl) x x0) u2
                                                  ((iso (THead (Flat Appl) x x0) u2)P:Prop.P
                                                       sn3 c (THead (Flat Appl) t0 u2))
                                        end of H8
                                        (H9
                                           we proceed by induction on H3 to prove 
                                              t3:T
                                                .(eq T t0 t3)P:Prop.P
                                                  (pr3 c t0 t3
                                                       (u2:T
                                                              .pr3 c (THead (Flat Appl) x x0) u2
                                                                ((iso (THead (Flat Appl) x x0) u2)P:Prop.P
                                                                     sn3 c (THead (Flat Appl) t3 u2))
                                                            sn3 c (THead (Flat Appl) t3 (THead (Flat Appl) x x0))))
                                              case refl_equal : 
                                                 the thesis becomes the hypothesis H6

                                              t3:T
                                                .(eq T t0 t3)P:Prop.P
                                                  (pr3 c t0 t3
                                                       (u2:T
                                                              .pr3 c (THead (Flat Appl) x x0) u2
                                                                ((iso (THead (Flat Appl) x x0) u2)P:Prop.P
                                                                     sn3 c (THead (Flat Appl) t3 u2))
                                                            sn3 c (THead (Flat Appl) t3 (THead (Flat Appl) x x0))))
                                        end of H9
                                        (H10
                                           we proceed by induction on H3 to prove 
                                              t3:T
                                                .(eq T (THead (Flat Appl) x x0) t3)P:Prop.P
                                                  (pr3 c (THead (Flat Appl) x x0) t3
                                                       x1:T
                                                            .x2:T
                                                              .eq T t3 (THead (Flat Appl) x1 x2)
                                                                v3:T
                                                                     .sn3 c v3
                                                                       (u2:T.(pr3 c t3 u2)((iso t3 u2)P:Prop.P)(sn3 c (THead (Flat Appl) v3 u2))
                                                                            sn3 c (THead (Flat Appl) v3 t3)))
                                              case refl_equal : 
                                                 the thesis becomes the hypothesis H2

                                              t3:T
                                                .(eq T (THead (Flat Appl) x x0) t3)P:Prop.P
                                                  (pr3 c (THead (Flat Appl) x x0) t3
                                                       x1:T
                                                            .x2:T
                                                              .eq T t3 (THead (Flat Appl) x1 x2)
                                                                v3:T
                                                                     .sn3 c v3
                                                                       (u2:T.(pr3 c t3 u2)((iso t3 u2)P:Prop.P)(sn3 c (THead (Flat Appl) v3 u2))
                                                                            sn3 c (THead (Flat Appl) v3 t3)))
                                        end of H10
                                        (H11
                                           we proceed by induction on H3 to prove 
                                              t3:T
                                                .(eq T (THead (Flat Appl) x x0) t3)P:Prop.P
                                                  (pr3 c (THead (Flat Appl) x x0) t3)(sn3 c t3)
                                              case refl_equal : 
                                                 the thesis becomes the hypothesis H1

                                              t3:T
                                                .(eq T (THead (Flat Appl) x x0) t3)P:Prop.P
                                                  (pr3 c (THead (Flat Appl) x x0) t3)(sn3 c t3)
                                        end of H11
                                         assume t3T
                                         suppose H12
                                            eq T (THead (Flat Appl) t0 (THead (Flat Appl) x x0)) t3
                                              P:Prop.P
                                         suppose H13pr2 c (THead (Flat Appl) t0 (THead (Flat Appl) x x0)) t3
                                           (H14
                                              by (pr2_gen_appl . . . . H13)

                                                 or3
                                                   ex3_2
                                                     T
                                                     T
                                                     λu2:T.λt2:T.eq T t3 (THead (Flat Appl) u2 t2)
                                                     λu2:T.λ:T.pr2 c t0 u2
                                                     λ:T.λt2:T.pr2 c (THead (Flat Appl) x x0) t2
                                                   ex4_4
                                                     T
                                                     T
                                                     T
                                                     T
                                                     λy1:T.λz1:T.λ:T.λ:T.eq T (THead (Flat Appl) x x0) (THead (Bind Abst) y1 z1)
                                                     λ:T.λ:T.λu2:T.λt2:T.eq T t3 (THead (Bind Abbr) u2 t2)
                                                     λ:T.λ:T.λu2:T.λ:T.pr2 c t0 u2
                                                     λ:T.λz1:T.λ:T.λt2:T.b:B.u:T.(pr2 (CHead c (Bind b) u) z1 t2)
                                                   ex6_6
                                                     B
                                                     T
                                                     T
                                                     T
                                                     T
                                                     T
                                                     λb:B.λ:T.λ:T.λ:T.λ:T.λ:T.not (eq B b Abst)
                                                     λb:B.λy1:T.λz1:T.λ:T.λ:T.λ:T.eq T (THead (Flat Appl) x x0) (THead (Bind b) y1 z1)
                                                     λb:B
                                                       .λ:T
                                                         .λ:T
                                                           .λz2:T
                                                             .λu2:T
                                                               .λy2:T.eq T t3 (THead (Bind b) y2 (THead (Flat Appl) (lift (S OO u2) z2))
                                                     λ:B.λ:T.λ:T.λ:T.λu2:T.λ:T.pr2 c t0 u2
                                                     λ:B.λy1:T.λ:T.λ:T.λ:T.λy2:T.pr2 c y1 y2
                                                     λb:B.λ:T.λz1:T.λz2:T.λ:T.λy2:T.pr2 (CHead c (Bind b) y2) z1 z2
                                           end of H14
                                           we proceed by induction on H14 to prove sn3 c t3
                                              case or3_intro0 : H15:ex3_2 T T λu2:T.λt4:T.eq T t3 (THead (Flat Appl) u2 t4) λu2:T.λ:T.pr2 c t0 u2 λ:T.λt4:T.pr2 c (THead (Flat Appl) x x0) t4 
                                                 the thesis becomes sn3 c t3
                                                    we proceed by induction on H15 to prove sn3 c t3
                                                       case ex3_2_intro : x1:T x2:T H16:eq T t3 (THead (Flat Appl) x1 x2) H17:pr2 c t0 x1 H18:pr2 c (THead (Flat Appl) x x0) x2 
                                                          the thesis becomes sn3 c t3
                                                             (H19
                                                                we proceed by induction on H16 to prove 
                                                                   (eq
                                                                       T
                                                                       THead (Flat Appl) t0 (THead (Flat Appl) x x0)
                                                                       THead (Flat Appl) x1 x2)
                                                                     P:Prop.P
                                                                   case refl_equal : 
                                                                      the thesis becomes the hypothesis H12

                                                                   (eq
                                                                       T
                                                                       THead (Flat Appl) t0 (THead (Flat Appl) x x0)
                                                                       THead (Flat Appl) x1 x2)
                                                                     P:Prop.P
                                                             end of H19
                                                             (H20
                                                                by (pr2_gen_appl . . . . H18)

                                                                   or3
                                                                     ex3_2 T T λu2:T.λt2:T.eq T x2 (THead (Flat Appl) u2 t2) λu2:T.λ:T.pr2 c x u2 λ:T.λt2:T.pr2 c x0 t2
                                                                     ex4_4
                                                                       T
                                                                       T
                                                                       T
                                                                       T
                                                                       λy1:T.λz1:T.λ:T.λ:T.eq T x0 (THead (Bind Abst) y1 z1)
                                                                       λ:T.λ:T.λu2:T.λt2:T.eq T x2 (THead (Bind Abbr) u2 t2)
                                                                       λ:T.λ:T.λu2:T.λ:T.pr2 c x u2
                                                                       λ:T.λz1:T.λ:T.λt2:T.b:B.u:T.(pr2 (CHead c (Bind b) u) z1 t2)
                                                                     ex6_6
                                                                       B
                                                                       T
                                                                       T
                                                                       T
                                                                       T
                                                                       T
                                                                       λb:B.λ:T.λ:T.λ:T.λ:T.λ:T.not (eq B b Abst)
                                                                       λb:B.λy1:T.λz1:T.λ:T.λ:T.λ:T.eq T x0 (THead (Bind b) y1 z1)
                                                                       λb:B
                                                                         .λ:T
                                                                           .λ:T
                                                                             .λz2:T
                                                                               .λu2:T
                                                                                 .λy2:T.eq T x2 (THead (Bind b) y2 (THead (Flat Appl) (lift (S OO u2) z2))
                                                                       λ:B.λ:T.λ:T.λ:T.λu2:T.λ:T.pr2 c x u2
                                                                       λ:B.λy1:T.λ:T.λ:T.λ:T.λy2:T.pr2 c y1 y2
                                                                       λb:B.λ:T.λz1:T.λz2:T.λ:T.λy2:T.pr2 (CHead c (Bind b) y2) z1 z2
                                                             end of H20
                                                             we proceed by induction on H20 to prove sn3 c (THead (Flat Appl) x1 x2)
                                                                case or3_intro0 : H21:ex3_2 T T λu2:T.λt4:T.eq T x2 (THead (Flat Appl) u2 t4) λu2:T.λ:T.pr2 c x u2 λ:T.λt4:T.pr2 c x0 t4 
                                                                   the thesis becomes sn3 c (THead (Flat Appl) x1 x2)
                                                                      we proceed by induction on H21 to prove sn3 c (THead (Flat Appl) x1 x2)
                                                                         case ex3_2_intro : x3:T x4:T H22:eq T x2 (THead (Flat Appl) x3 x4) H23:pr2 c x x3 H24:pr2 c x0 x4 
                                                                            the thesis becomes sn3 c (THead (Flat Appl) x1 x2)
                                                                               (H25
                                                                                  we proceed by induction on H22 to prove 
                                                                                     (eq
                                                                                         T
                                                                                         THead (Flat Appl) t0 (THead (Flat Appl) x x0)
                                                                                         THead (Flat Appl) x1 (THead (Flat Appl) x3 x4))
                                                                                       P:Prop.P
                                                                                     case refl_equal : 
                                                                                        the thesis becomes the hypothesis H19

                                                                                     (eq
                                                                                         T
                                                                                         THead (Flat Appl) t0 (THead (Flat Appl) x x0)
                                                                                         THead (Flat Appl) x1 (THead (Flat Appl) x3 x4))
                                                                                       P:Prop.P
                                                                               end of H25
                                                                               (H_x
                                                                                  by (term_dec . .)

                                                                                     or
                                                                                       eq T (THead (Flat Appl) x x0) (THead (Flat Appl) x3 x4)
                                                                                       eq T (THead (Flat Appl) x x0) (THead (Flat Appl) x3 x4)
                                                                                         P:Prop.P
                                                                               end of H_x
                                                                               (H26consider H_x
                                                                               we proceed by induction on H26 to prove sn3 c (THead (Flat Appl) x1 (THead (Flat Appl) x3 x4))
                                                                                  case or_introl : H27:eq T (THead (Flat Appl) x x0) (THead (Flat Appl) x3 x4) 
                                                                                     the thesis becomes sn3 c (THead (Flat Appl) x1 (THead (Flat Appl) x3 x4))
                                                                                        (H28
                                                                                           by (f_equal . . . . . H27)
                                                                                           we proved 
                                                                                              eq
                                                                                                T
                                                                                                <λ:T.T>
                                                                                                  CASE THead (Flat Appl) x x0 OF
                                                                                                    TSort x
                                                                                                  | TLRef x
                                                                                                  | THead  t t
                                                                                                <λ:T.T>
                                                                                                  CASE THead (Flat Appl) x3 x4 OF
                                                                                                    TSort x
                                                                                                  | TLRef x
                                                                                                  | THead  t t

                                                                                              eq
                                                                                                T
                                                                                                λe:T.<λ:T.T> CASE e OF TSort x | TLRef x | THead  t t
                                                                                                  THead (Flat Appl) x x0
                                                                                                λe:T.<λ:T.T> CASE e OF TSort x | TLRef x | THead  t t
                                                                                                  THead (Flat Appl) x3 x4
                                                                                        end of H28
                                                                                        (h1
                                                                                           (H29
                                                                                              by (f_equal . . . . . H27)
                                                                                              we proved 
                                                                                                 eq
                                                                                                   T
                                                                                                   <λ:T.T> CASE THead (Flat Appl) x x0 OF TSort x0 | TLRef x0 | THead   tt
                                                                                                   <λ:T.T> CASE THead (Flat Appl) x3 x4 OF TSort x0 | TLRef x0 | THead   tt

                                                                                                 eq
                                                                                                   T
                                                                                                   λe:T.<λ:T.T> CASE e OF TSort x0 | TLRef x0 | THead   tt
                                                                                                     THead (Flat Appl) x x0
                                                                                                   λe:T.<λ:T.T> CASE e OF TSort x0 | TLRef x0 | THead   tt
                                                                                                     THead (Flat Appl) x3 x4
                                                                                           end of H29
                                                                                           suppose H30eq T x x3
                                                                                              (H31
                                                                                                 consider H29
                                                                                                 we proved 
                                                                                                    eq
                                                                                                      T
                                                                                                      <λ:T.T> CASE THead (Flat Appl) x x0 OF TSort x0 | TLRef x0 | THead   tt
                                                                                                      <λ:T.T> CASE THead (Flat Appl) x3 x4 OF TSort x0 | TLRef x0 | THead   tt
                                                                                                 that is equivalent to eq T x0 x4
                                                                                                 by (eq_ind_r . . . H25 . previous)

                                                                                                    (eq
                                                                                                        T
                                                                                                        THead (Flat Appl) t0 (THead (Flat Appl) x x0)
                                                                                                        THead (Flat Appl) x1 (THead (Flat Appl) x3 x0))
                                                                                                      P:Prop.P
                                                                                              end of H31
                                                                                              consider H29
                                                                                              we proved 
                                                                                                 eq
                                                                                                   T
                                                                                                   <λ:T.T> CASE THead (Flat Appl) x x0 OF TSort x0 | TLRef x0 | THead   tt
                                                                                                   <λ:T.T> CASE THead (Flat Appl) x3 x4 OF TSort x0 | TLRef x0 | THead   tt
                                                                                              that is equivalent to eq T x0 x4
                                                                                              we proceed by induction on the previous result to prove sn3 c (THead (Flat Appl) x1 (THead (Flat Appl) x3 x4))
                                                                                                 case refl_equal : 
                                                                                                    the thesis becomes sn3 c (THead (Flat Appl) x1 (THead (Flat Appl) x3 x0))
                                                                                                       (H33
                                                                                                          by (eq_ind_r . . . H31 . H30)

                                                                                                             (eq
                                                                                                                 T
                                                                                                                 THead (Flat Appl) t0 (THead (Flat Appl) x x0)
                                                                                                                 THead (Flat Appl) x1 (THead (Flat Appl) x x0))
                                                                                                               P:Prop.P
                                                                                                       end of H33
                                                                                                       we proceed by induction on H30 to prove sn3 c (THead (Flat Appl) x1 (THead (Flat Appl) x3 x0))
                                                                                                          case refl_equal : 
                                                                                                             the thesis becomes sn3 c (THead (Flat Appl) x1 (THead (Flat Appl) x x0))
                                                                                                                (H_x0
                                                                                                                   by (term_dec . .)
or (eq T t0 x1) (eq T t0 x1)P:Prop.P
                                                                                                                end of H_x0
                                                                                                                (H35consider H_x0
                                                                                                                we proceed by induction on H35 to prove sn3 c (THead (Flat Appl) x1 (THead (Flat Appl) x x0))
                                                                                                                   case or_introl : H36:eq T t0 x1 
                                                                                                                      the thesis becomes sn3 c (THead (Flat Appl) x1 (THead (Flat Appl) x x0))
                                                                                                                         (H37
                                                                                                                            by (eq_ind_r . . . H33 . H36)

                                                                                                                               (eq
                                                                                                                                   T
                                                                                                                                   THead (Flat Appl) t0 (THead (Flat Appl) x x0)
                                                                                                                                   THead (Flat Appl) t0 (THead (Flat Appl) x x0))
                                                                                                                                 P:Prop.P
                                                                                                                         end of H37
                                                                                                                         we proceed by induction on H36 to prove sn3 c (THead (Flat Appl) x1 (THead (Flat Appl) x x0))
                                                                                                                            case refl_equal : 
                                                                                                                               the thesis becomes sn3 c (THead (Flat Appl) t0 (THead (Flat Appl) x x0))
                                                                                                                                  by (refl_equal . .)
                                                                                                                                  we proved 
                                                                                                                                     eq
                                                                                                                                       T
                                                                                                                                       THead (Flat Appl) t0 (THead (Flat Appl) x x0)
                                                                                                                                       THead (Flat Appl) t0 (THead (Flat Appl) x x0)
                                                                                                                                  by (H37 previous .)
sn3 c (THead (Flat Appl) t0 (THead (Flat Appl) x x0))
sn3 c (THead (Flat Appl) x1 (THead (Flat Appl) x x0))
                                                                                                                   case or_intror : H36:(eq T t0 x1)P:Prop.P 
                                                                                                                      the thesis becomes sn3 c (THead (Flat Appl) x1 (THead (Flat Appl) x x0))
                                                                                                                         (h1by (pr3_pr2 . . . H17) we proved pr3 c t0 x1
                                                                                                                         (h2
                                                                                                                             assume u2T
                                                                                                                             suppose H37pr3 c (THead (Flat Appl) x x0) u2
                                                                                                                             suppose H38(iso (THead (Flat Appl) x x0) u2)P:Prop.P
                                                                                                                               (h1
                                                                                                                                  by (H8 . H37 H38)
sn3 c (THead (Flat Appl) t0 u2)
                                                                                                                               end of h1
                                                                                                                               (h2
                                                                                                                                  by (pr2_head_1 . . . H17 . .)
                                                                                                                                  we proved pr2 c (THead (Flat Appl) t0 u2) (THead (Flat Appl) x1 u2)
                                                                                                                                  by (pr3_pr2 . . . previous)
pr3 c (THead (Flat Appl) t0 u2) (THead (Flat Appl) x1 u2)
                                                                                                                               end of h2
                                                                                                                               by (sn3_pr3_trans . . h1 . h2)
                                                                                                                               we proved sn3 c (THead (Flat Appl) x1 u2)

                                                                                                                               u2:T
                                                                                                                                 .pr3 c (THead (Flat Appl) x x0) u2
                                                                                                                                   ((iso (THead (Flat Appl) x x0) u2)P:Prop.P
                                                                                                                                        sn3 c (THead (Flat Appl) x1 u2))
                                                                                                                         end of h2
                                                                                                                         by (H9 . H36 h1 h2)
sn3 c (THead (Flat Appl) x1 (THead (Flat Appl) x x0))
sn3 c (THead (Flat Appl) x1 (THead (Flat Appl) x x0))
sn3 c (THead (Flat Appl) x1 (THead (Flat Appl) x3 x0))
                                                                                              we proved sn3 c (THead (Flat Appl) x1 (THead (Flat Appl) x3 x4))
(eq T x x3)(sn3 c (THead (Flat Appl) x1 (THead (Flat Appl) x3 x4)))
                                                                                        end of h1
                                                                                        (h2
                                                                                           consider H28
                                                                                           we proved 
                                                                                              eq
                                                                                                T
                                                                                                <λ:T.T>
                                                                                                  CASE THead (Flat Appl) x x0 OF
                                                                                                    TSort x
                                                                                                  | TLRef x
                                                                                                  | THead  t t
                                                                                                <λ:T.T>
                                                                                                  CASE THead (Flat Appl) x3 x4 OF
                                                                                                    TSort x
                                                                                                  | TLRef x
                                                                                                  | THead  t t
eq T x x3
                                                                                        end of h2
                                                                                        by (h1 h2)
sn3 c (THead (Flat Appl) x1 (THead (Flat Appl) x3 x4))
                                                                                  case or_intror : H27:(eq T (THead (Flat Appl) x x0) (THead (Flat Appl) x3 x4))P:Prop.P 
                                                                                     the thesis becomes sn3 c (THead (Flat Appl) x1 (THead (Flat Appl) x3 x4))
                                                                                        (h1
                                                                                           (h1by (pr3_pr2 . . . H23) we proved pr3 c x x3
                                                                                           (h2by (pr3_pr2 . . . H24) we proved pr3 c x0 x4
                                                                                           by (pr3_flat . . . h1 . . h2 .)
pr3 c (THead (Flat Appl) x x0) (THead (Flat Appl) x3 x4)
                                                                                        end of h1
                                                                                        (h2
                                                                                           by (refl_equal . .)
eq T (THead (Flat Appl) x3 x4) (THead (Flat Appl) x3 x4)
                                                                                        end of h2
                                                                                        (h3
                                                                                           (h1by (sn3_sing . . H5) we proved sn3 c t0
                                                                                           (h2by (pr3_pr2 . . . H17) we proved pr3 c t0 x1
                                                                                           by (sn3_pr3_trans . . h1 . h2)
sn3 c x1
                                                                                        end of h3
                                                                                        (h4
                                                                                            assume u2T
                                                                                            suppose H28pr3 c (THead (Flat Appl) x3 x4) u2
                                                                                            suppose H29(iso (THead (Flat Appl) x3 x4) u2)P:Prop.P
                                                                                              (h1
                                                                                                 (h1
                                                                                                    (h1
                                                                                                       by (pr2_thin_dx . . . H24 . .)
pr2 c (THead (Flat Appl) x x0) (THead (Flat Appl) x x4)
                                                                                                    end of h1
                                                                                                    (h2
                                                                                                       by (pr2_head_1 . . . H23 . .)
                                                                                                       we proved pr2 c (THead (Flat Appl) x x4) (THead (Flat Appl) x3 x4)
                                                                                                       by (pr3_sing . . . previous . H28)
pr3 c (THead (Flat Appl) x x4) u2
                                                                                                    end of h2
                                                                                                    by (pr3_sing . . . h1 . h2)
pr3 c (THead (Flat Appl) x x0) u2
                                                                                                 end of h1
                                                                                                 (h2
                                                                                                     suppose H30iso (THead (Flat Appl) x x0) u2
                                                                                                     assume PProp
                                                                                                       by (iso_head . . . . .)
                                                                                                       we proved iso (THead (Flat Appl) x3 x4) (THead (Flat Appl) x x0)
                                                                                                       by (iso_trans . . previous . H30)
                                                                                                       we proved iso (THead (Flat Appl) x3 x4) u2
                                                                                                       by (H29 previous .)
                                                                                                       we proved P
(iso (THead (Flat Appl) x x0) u2)P:Prop.P
                                                                                                 end of h2
                                                                                                 by (H8 . h1 h2)
sn3 c (THead (Flat Appl) t0 u2)
                                                                                              end of h1
                                                                                              (h2
                                                                                                 by (pr2_head_1 . . . H17 . .)
                                                                                                 we proved pr2 c (THead (Flat Appl) t0 u2) (THead (Flat Appl) x1 u2)
                                                                                                 by (pr3_pr2 . . . previous)
pr3 c (THead (Flat Appl) t0 u2) (THead (Flat Appl) x1 u2)
                                                                                              end of h2
                                                                                              by (sn3_pr3_trans . . h1 . h2)
                                                                                              we proved sn3 c (THead (Flat Appl) x1 u2)

                                                                                              u2:T
                                                                                                .pr3 c (THead (Flat Appl) x3 x4) u2
                                                                                                  ((iso (THead (Flat Appl) x3 x4) u2)P:Prop.P
                                                                                                       sn3 c (THead (Flat Appl) x1 u2))
                                                                                        end of h4
                                                                                        by (H10 . H27 h1 . . h2 . h3 h4)
sn3 c (THead (Flat Appl) x1 (THead (Flat Appl) x3 x4))
                                                                               we proved sn3 c (THead (Flat Appl) x1 (THead (Flat Appl) x3 x4))
                                                                               by (eq_ind_r . . . previous . H22)
sn3 c (THead (Flat Appl) x1 x2)
sn3 c (THead (Flat Appl) x1 x2)
                                                                case or3_intro1 : H21:ex4_4 T T T T λy1:T.λz1:T.λ:T.λ:T.eq T x0 (THead (Bind Abst) y1 z1) λ:T.λ:T.λu2:T.λt4:T.eq T x2 (THead (Bind Abbr) u2 t4) λ:T.λ:T.λu2:T.λ:T.pr2 c x u2 λ:T.λz1:T.λ:T.λt4:T.b:B.u:T.(pr2 (CHead c (Bind b) u) z1 t4) 
                                                                   the thesis becomes sn3 c (THead (Flat Appl) x1 x2)
                                                                      we proceed by induction on H21 to prove sn3 c (THead (Flat Appl) x1 x2)
                                                                         case ex4_4_intro : x3:T x4:T x5:T x6:T H22:eq T x0 (THead (Bind Abst) x3 x4) H23:eq T x2 (THead (Bind Abbr) x5 x6) H24:pr2 c x x5 H25:b:B.u:T.(pr2 (CHead c (Bind b) u) x4 x6) 
                                                                            the thesis becomes sn3 c (THead (Flat Appl) x1 x2)
                                                                               (H26
                                                                                  we proceed by induction on H23 to prove 
                                                                                     (eq
                                                                                         T
                                                                                         THead (Flat Appl) t0 (THead (Flat Appl) x x0)
                                                                                         THead (Flat Appl) x1 (THead (Bind Abbr) x5 x6))
                                                                                       P:Prop.P
                                                                                     case refl_equal : 
                                                                                        the thesis becomes the hypothesis H19

                                                                                     (eq
                                                                                         T
                                                                                         THead (Flat Appl) t0 (THead (Flat Appl) x x0)
                                                                                         THead (Flat Appl) x1 (THead (Bind Abbr) x5 x6))
                                                                                       P:Prop.P
                                                                               end of H26
                                                                               (H30
                                                                                  we proceed by induction on H22 to prove 
                                                                                     u2:T
                                                                                       .pr3 c (THead (Flat Appl) x (THead (Bind Abst) x3 x4)) u2
                                                                                         (iso (THead (Flat Appl) x (THead (Bind Abst) x3 x4)) u2
                                                                                                P:Prop.P
                                                                                              sn3 c (THead (Flat Appl) t0 u2))
                                                                                     case refl_equal : 
                                                                                        the thesis becomes the hypothesis H8

                                                                                     u2:T
                                                                                       .pr3 c (THead (Flat Appl) x (THead (Bind Abst) x3 x4)) u2
                                                                                         (iso (THead (Flat Appl) x (THead (Bind Abst) x3 x4)) u2
                                                                                                P:Prop.P
                                                                                              sn3 c (THead (Flat Appl) t0 u2))
                                                                               end of H30
                                                                               (h1
                                                                                  (h1
                                                                                     (h1
                                                                                        (h1by (pr0_refl .) we proved pr0 x x
                                                                                        (h2by (pr0_refl .) we proved pr0 x4 x4
                                                                                        by (pr0_beta . . . h1 . . h2)
                                                                                        we proved 
                                                                                           pr0
                                                                                             THead (Flat Appl) x (THead (Bind Abst) x3 x4)
                                                                                             THead (Bind Abbr) x x4
                                                                                        by (pr2_free . . . previous)

                                                                                           pr2
                                                                                             c
                                                                                             THead (Flat Appl) x (THead (Bind Abst) x3 x4)
                                                                                             THead (Bind Abbr) x x4
                                                                                     end of h1
                                                                                     (h2
                                                                                        (h1by (pr3_pr2 . . . H24) we proved pr3 c x x5
                                                                                        (h2
                                                                                           by (H25 . .)
                                                                                           we proved pr2 (CHead c (Bind Abbr) x5) x4 x6
                                                                                           by (pr3_pr2 . . . previous)
pr3 (CHead c (Bind Abbr) x5) x4 x6
                                                                                        end of h2
                                                                                        by (pr3_head_12 . . . h1 . . . h2)
pr3 c (THead (Bind Abbr) x x4) (THead (Bind Abbr) x5 x6)
                                                                                     end of h2
                                                                                     by (pr3_sing . . . h1 . h2)

                                                                                        pr3
                                                                                          c
                                                                                          THead (Flat Appl) x (THead (Bind Abst) x3 x4)
                                                                                          THead (Bind Abbr) x5 x6
                                                                                  end of h1
                                                                                  (h2
                                                                                      suppose H32
                                                                                         iso
                                                                                           THead (Flat Appl) x (THead (Bind Abst) x3 x4)
                                                                                           THead (Bind Abbr) x5 x6
                                                                                      assume PProp
                                                                                        (H33
                                                                                           by cases on H32 we prove 
                                                                                              (eq
                                                                                                  T
                                                                                                  THead (Flat Appl) x (THead (Bind Abst) x3 x4)
                                                                                                  THead (Flat Appl) x (THead (Bind Abst) x3 x4))
                                                                                                (eq T (THead (Bind Abbr) x5 x6) (THead (Bind Abbr) x5 x6))P
                                                                                              case iso_sort n1:nat n2:nat 
                                                                                                 the thesis becomes 
                                                                                                       H33:eq T (TSort n1) (THead (Flat Appl) x (THead (Bind Abst) x3 x4))
                                                                                                         .H34:(eq T (TSort n2) (THead (Bind Abbr) x5 x6)).P
                                                                                                  suppose H33eq T (TSort n1) (THead (Flat Appl) x (THead (Bind Abst) x3 x4))
                                                                                                  suppose H34eq T (TSort n2) (THead (Bind Abbr) x5 x6)
                                                                                                    (H35
                                                                                                       we proceed by induction on H33 to prove 
                                                                                                          <λ:T.Prop>
                                                                                                            CASE THead (Flat Appl) x (THead (Bind Abst) x3 x4) OF
                                                                                                              TSort True
                                                                                                            | TLRef False
                                                                                                            | THead   False
                                                                                                          case refl_equal : 
                                                                                                             the thesis becomes 
                                                                                                             <λ:T.Prop>
                                                                                                               CASE TSort n1 OF
                                                                                                                 TSort True
                                                                                                               | TLRef False
                                                                                                               | THead   False
                                                                                                                consider I
                                                                                                                we proved True

                                                                                                                   <λ:T.Prop>
                                                                                                                     CASE TSort n1 OF
                                                                                                                       TSort True
                                                                                                                     | TLRef False
                                                                                                                     | THead   False

                                                                                                          <λ:T.Prop>
                                                                                                            CASE THead (Flat Appl) x (THead (Bind Abst) x3 x4) OF
                                                                                                              TSort True
                                                                                                            | TLRef False
                                                                                                            | THead   False
                                                                                                    end of H35
                                                                                                    consider H35
                                                                                                    we proved 
                                                                                                       <λ:T.Prop>
                                                                                                         CASE THead (Flat Appl) x (THead (Bind Abst) x3 x4) OF
                                                                                                           TSort True
                                                                                                         | TLRef False
                                                                                                         | THead   False
                                                                                                    that is equivalent to False
                                                                                                    we proceed by induction on the previous result to prove (eq T (TSort n2) (THead (Bind Abbr) x5 x6))P
                                                                                                    we proved (eq T (TSort n2) (THead (Bind Abbr) x5 x6))P
                                                                                                    by (previous H34)
                                                                                                    we proved P

                                                                                                    H33:eq T (TSort n1) (THead (Flat Appl) x (THead (Bind Abst) x3 x4))
                                                                                                      .H34:(eq T (TSort n2) (THead (Bind Abbr) x5 x6)).P
                                                                                              case iso_lref i1:nat i2:nat 
                                                                                                 the thesis becomes 
                                                                                                       H33:eq T (TLRef i1) (THead (Flat Appl) x (THead (Bind Abst) x3 x4))
                                                                                                         .H34:(eq T (TLRef i2) (THead (Bind Abbr) x5 x6)).P
                                                                                                  suppose H33eq T (TLRef i1) (THead (Flat Appl) x (THead (Bind Abst) x3 x4))
                                                                                                  suppose H34eq T (TLRef i2) (THead (Bind Abbr) x5 x6)
                                                                                                    (H35
                                                                                                       we proceed by induction on H33 to prove 
                                                                                                          <λ:T.Prop>
                                                                                                            CASE THead (Flat Appl) x (THead (Bind Abst) x3 x4) OF
                                                                                                              TSort False
                                                                                                            | TLRef True
                                                                                                            | THead   False
                                                                                                          case refl_equal : 
                                                                                                             the thesis becomes 
                                                                                                             <λ:T.Prop>
                                                                                                               CASE TLRef i1 OF
                                                                                                                 TSort False
                                                                                                               | TLRef True
                                                                                                               | THead   False
                                                                                                                consider I
                                                                                                                we proved True

                                                                                                                   <λ:T.Prop>
                                                                                                                     CASE TLRef i1 OF
                                                                                                                       TSort False
                                                                                                                     | TLRef True
                                                                                                                     | THead   False

                                                                                                          <λ:T.Prop>
                                                                                                            CASE THead (Flat Appl) x (THead (Bind Abst) x3 x4) OF
                                                                                                              TSort False
                                                                                                            | TLRef True
                                                                                                            | THead   False
                                                                                                    end of H35
                                                                                                    consider H35
                                                                                                    we proved 
                                                                                                       <λ:T.Prop>
                                                                                                         CASE THead (Flat Appl) x (THead (Bind Abst) x3 x4) OF
                                                                                                           TSort False
                                                                                                         | TLRef True
                                                                                                         | THead   False
                                                                                                    that is equivalent to False
                                                                                                    we proceed by induction on the previous result to prove (eq T (TLRef i2) (THead (Bind Abbr) x5 x6))P
                                                                                                    we proved (eq T (TLRef i2) (THead (Bind Abbr) x5 x6))P
                                                                                                    by (previous H34)
                                                                                                    we proved P

                                                                                                    H33:eq T (TLRef i1) (THead (Flat Appl) x (THead (Bind Abst) x3 x4))
                                                                                                      .H34:(eq T (TLRef i2) (THead (Bind Abbr) x5 x6)).P
                                                                                              case iso_head v4:T v5:T t4:T t5:T k:K 
                                                                                                 the thesis becomes 
                                                                                                       H33:eq T (THead k v4 t4) (THead (Flat Appl) x (THead (Bind Abst) x3 x4))
                                                                                                         .H34:(eq T (THead k v5 t5) (THead (Bind Abbr) x5 x6)).P
                                                                                                  suppose H33eq T (THead k v4 t4) (THead (Flat Appl) x (THead (Bind Abst) x3 x4))
                                                                                                  suppose H34eq T (THead k v5 t5) (THead (Bind Abbr) x5 x6)
                                                                                                    (H35
                                                                                                       by (f_equal . . . . . H33)
                                                                                                       we proved 
                                                                                                          eq
                                                                                                            T
                                                                                                            <λ:T.T> CASE THead k v4 t4 OF TSort t4 | TLRef t4 | THead   tt
                                                                                                            <λ:T.T>
                                                                                                              CASE THead (Flat Appl) x (THead (Bind Abst) x3 x4) OF
                                                                                                                TSort t4
                                                                                                              | TLRef t4
                                                                                                              | THead   tt

                                                                                                          eq
                                                                                                            T
                                                                                                            λe:T.<λ:T.T> CASE e OF TSort t4 | TLRef t4 | THead   tt (THead k v4 t4)
                                                                                                            λe:T.<λ:T.T> CASE e OF TSort t4 | TLRef t4 | THead   tt
                                                                                                              THead (Flat Appl) x (THead (Bind Abst) x3 x4)
                                                                                                    end of H35
                                                                                                    (h1
                                                                                                       (H36
                                                                                                          by (f_equal . . . . . H33)
                                                                                                          we proved 
                                                                                                             eq
                                                                                                               T
                                                                                                               <λ:T.T> CASE THead k v4 t4 OF TSort v4 | TLRef v4 | THead  t t
                                                                                                               <λ:T.T>
                                                                                                                 CASE THead (Flat Appl) x (THead (Bind Abst) x3 x4) OF
                                                                                                                   TSort v4
                                                                                                                 | TLRef v4
                                                                                                                 | THead  t t

                                                                                                             eq
                                                                                                               T
                                                                                                               λe:T.<λ:T.T> CASE e OF TSort v4 | TLRef v4 | THead  t t (THead k v4 t4)
                                                                                                               λe:T.<λ:T.T> CASE e OF TSort v4 | TLRef v4 | THead  t t
                                                                                                                 THead (Flat Appl) x (THead (Bind Abst) x3 x4)
                                                                                                       end of H36
                                                                                                       (h1
                                                                                                          (H37
                                                                                                             by (f_equal . . . . . H33)
                                                                                                             we proved 
                                                                                                                eq
                                                                                                                  K
                                                                                                                  <λ:T.K> CASE THead k v4 t4 OF TSort k | TLRef k | THead k0  k0
                                                                                                                  <λ:T.K>
                                                                                                                    CASE THead (Flat Appl) x (THead (Bind Abst) x3 x4) OF
                                                                                                                      TSort k
                                                                                                                    | TLRef k
                                                                                                                    | THead k0  k0

                                                                                                                eq
                                                                                                                  K
                                                                                                                  λe:T.<λ:T.K> CASE e OF TSort k | TLRef k | THead k0  k0 (THead k v4 t4)
                                                                                                                  λe:T.<λ:T.K> CASE e OF TSort k | TLRef k | THead k0  k0
                                                                                                                    THead (Flat Appl) x (THead (Bind Abst) x3 x4)
                                                                                                          end of H37
                                                                                                          consider H37
                                                                                                          we proved 
                                                                                                             eq
                                                                                                               K
                                                                                                               <λ:T.K> CASE THead k v4 t4 OF TSort k | TLRef k | THead k0  k0
                                                                                                               <λ:T.K>
                                                                                                                 CASE THead (Flat Appl) x (THead (Bind Abst) x3 x4) OF
                                                                                                                   TSort k
                                                                                                                 | TLRef k
                                                                                                                 | THead k0  k0
                                                                                                          that is equivalent to eq K k (Flat Appl)
                                                                                                          by (sym_eq . . . previous)
                                                                                                          we proved eq K (Flat Appl) k
                                                                                                          we proceed by induction on the previous result to prove 
                                                                                                             eq T v4 x
                                                                                                               (eq T t4 (THead (Bind Abst) x3 x4)
                                                                                                                    (eq T (THead k v5 t5) (THead (Bind Abbr) x5 x6))P)
                                                                                                             case refl_equal : 
                                                                                                                the thesis becomes 
                                                                                                                eq T v4 x
                                                                                                                  (eq T t4 (THead (Bind Abst) x3 x4)
                                                                                                                       (eq T (THead (Flat Appl) v5 t5) (THead (Bind Abbr) x5 x6))P)
                                                                                                                   suppose H38eq T v4 x
                                                                                                                      by (sym_eq . . . H38)
                                                                                                                      we proved eq T x v4
                                                                                                                      we proceed by induction on the previous result to prove 
                                                                                                                         eq T t4 (THead (Bind Abst) x3 x4)
                                                                                                                           (eq T (THead (Flat Appl) v5 t5) (THead (Bind Abbr) x5 x6))P
                                                                                                                         case refl_equal : 
                                                                                                                            the thesis becomes 
                                                                                                                            eq T t4 (THead (Bind Abst) x3 x4)
                                                                                                                              (eq T (THead (Flat Appl) v5 t5) (THead (Bind Abbr) x5 x6))P
                                                                                                                               suppose H39eq T t4 (THead (Bind Abst) x3 x4)
                                                                                                                                  by (sym_eq . . . H39)
                                                                                                                                  we proved eq T (THead (Bind Abst) x3 x4) t4
                                                                                                                                  we proceed by induction on the previous result to prove (eq T (THead (Flat Appl) v5 t5) (THead (Bind Abbr) x5 x6))P
                                                                                                                                     case refl_equal : 
                                                                                                                                        the thesis becomes (eq T (THead (Flat Appl) v5 t5) (THead (Bind Abbr) x5 x6))P
                                                                                                                                           suppose H40eq T (THead (Flat Appl) v5 t5) (THead (Bind Abbr) x5 x6)
                                                                                                                                              (H41
                                                                                                                                                 we proceed by induction on H40 to prove 
                                                                                                                                                    <λ:T.Prop>
                                                                                                                                                      CASE THead (Bind Abbr) x5 x6 OF
                                                                                                                                                        TSort False
                                                                                                                                                      | TLRef False
                                                                                                                                                      | THead k0  <λ:K.Prop> CASE k0 OF Bind False | Flat True
                                                                                                                                                    case refl_equal : 
                                                                                                                                                       the thesis becomes 
                                                                                                                                                       <λ:T.Prop>
                                                                                                                                                         CASE THead (Flat Appl) v5 t5 OF
                                                                                                                                                           TSort False
                                                                                                                                                         | TLRef False
                                                                                                                                                         | THead k0  <λ:K.Prop> CASE k0 OF Bind False | Flat True
                                                                                                                                                          consider I
                                                                                                                                                          we proved True

                                                                                                                                                             <λ:T.Prop>
                                                                                                                                                               CASE THead (Flat Appl) v5 t5 OF
                                                                                                                                                                 TSort False
                                                                                                                                                               | TLRef False
                                                                                                                                                               | THead k0  <λ:K.Prop> CASE k0 OF Bind False | Flat True

                                                                                                                                                    <λ:T.Prop>
                                                                                                                                                      CASE THead (Bind Abbr) x5 x6 OF
                                                                                                                                                        TSort False
                                                                                                                                                      | TLRef False
                                                                                                                                                      | THead k0  <λ:K.Prop> CASE k0 OF Bind False | Flat True
                                                                                                                                              end of H41
                                                                                                                                              consider H41
                                                                                                                                              we proved 
                                                                                                                                                 <λ:T.Prop>
                                                                                                                                                   CASE THead (Bind Abbr) x5 x6 OF
                                                                                                                                                     TSort False
                                                                                                                                                   | TLRef False
                                                                                                                                                   | THead k0  <λ:K.Prop> CASE k0 OF Bind False | Flat True
                                                                                                                                              that is equivalent to False
                                                                                                                                              we proceed by induction on the previous result to prove P
                                                                                                                                              we proved P
(eq T (THead (Flat Appl) v5 t5) (THead (Bind Abbr) x5 x6))P
                                                                                                                                  we proved (eq T (THead (Flat Appl) v5 t5) (THead (Bind Abbr) x5 x6))P

                                                                                                                                  eq T t4 (THead (Bind Abst) x3 x4)
                                                                                                                                    (eq T (THead (Flat Appl) v5 t5) (THead (Bind Abbr) x5 x6))P
                                                                                                                      we proved 
                                                                                                                         eq T t4 (THead (Bind Abst) x3 x4)
                                                                                                                           (eq T (THead (Flat Appl) v5 t5) (THead (Bind Abbr) x5 x6))P

                                                                                                                      eq T v4 x
                                                                                                                        (eq T t4 (THead (Bind Abst) x3 x4)
                                                                                                                             (eq T (THead (Flat Appl) v5 t5) (THead (Bind Abbr) x5 x6))P)

                                                                                                             eq T v4 x
                                                                                                               (eq T t4 (THead (Bind Abst) x3 x4)
                                                                                                                    (eq T (THead k v5 t5) (THead (Bind Abbr) x5 x6))P)
                                                                                                       end of h1
                                                                                                       (h2
                                                                                                          consider H36
                                                                                                          we proved 
                                                                                                             eq
                                                                                                               T
                                                                                                               <λ:T.T> CASE THead k v4 t4 OF TSort v4 | TLRef v4 | THead  t t
                                                                                                               <λ:T.T>
                                                                                                                 CASE THead (Flat Appl) x (THead (Bind Abst) x3 x4) OF
                                                                                                                   TSort v4
                                                                                                                 | TLRef v4
                                                                                                                 | THead  t t
eq T v4 x
                                                                                                       end of h2
                                                                                                       by (h1 h2)

                                                                                                          eq T t4 (THead (Bind Abst) x3 x4)
                                                                                                            (eq T (THead k v5 t5) (THead (Bind Abbr) x5 x6))P
                                                                                                    end of h1
                                                                                                    (h2
                                                                                                       consider H35
                                                                                                       we proved 
                                                                                                          eq
                                                                                                            T
                                                                                                            <λ:T.T> CASE THead k v4 t4 OF TSort t4 | TLRef t4 | THead   tt
                                                                                                            <λ:T.T>
                                                                                                              CASE THead (Flat Appl) x (THead (Bind Abst) x3 x4) OF
                                                                                                                TSort t4
                                                                                                              | TLRef t4
                                                                                                              | THead   tt
eq T t4 (THead (Bind Abst) x3 x4)
                                                                                                    end of h2
                                                                                                    by (h1 h2)
                                                                                                    we proved (eq T (THead k v5 t5) (THead (Bind Abbr) x5 x6))P
                                                                                                    by (previous H34)
                                                                                                    we proved P

                                                                                                    H33:eq T (THead k v4 t4) (THead (Flat Appl) x (THead (Bind Abst) x3 x4))
                                                                                                      .H34:(eq T (THead k v5 t5) (THead (Bind Abbr) x5 x6)).P

                                                                                              (eq
                                                                                                  T
                                                                                                  THead (Flat Appl) x (THead (Bind Abst) x3 x4)
                                                                                                  THead (Flat Appl) x (THead (Bind Abst) x3 x4))
                                                                                                (eq T (THead (Bind Abbr) x5 x6) (THead (Bind Abbr) x5 x6))P
                                                                                        end of H33
                                                                                        (h1
                                                                                           by (refl_equal . .)

                                                                                              eq
                                                                                                T
                                                                                                THead (Flat Appl) x (THead (Bind Abst) x3 x4)
                                                                                                THead (Flat Appl) x (THead (Bind Abst) x3 x4)
                                                                                        end of h1
                                                                                        (h2
                                                                                           by (refl_equal . .)
eq T (THead (Bind Abbr) x5 x6) (THead (Bind Abbr) x5 x6)
                                                                                        end of h2
                                                                                        by (H33 h1 h2)
                                                                                        we proved P

                                                                                        (iso
                                                                                            THead (Flat Appl) x (THead (Bind Abst) x3 x4)
                                                                                            THead (Bind Abbr) x5 x6)
                                                                                          P:Prop.P
                                                                                  end of h2
                                                                                  by (H30 . h1 h2)
sn3 c (THead (Flat Appl) t0 (THead (Bind Abbr) x5 x6))
                                                                               end of h1
                                                                               (h2
                                                                                  by (pr2_head_1 . . . H17 . .)
                                                                                  we proved 
                                                                                     pr2
                                                                                       c
                                                                                       THead (Flat Appl) t0 (THead (Bind Abbr) x5 x6)
                                                                                       THead (Flat Appl) x1 (THead (Bind Abbr) x5 x6)
                                                                                  by (pr3_pr2 . . . previous)

                                                                                     pr3
                                                                                       c
                                                                                       THead (Flat Appl) t0 (THead (Bind Abbr) x5 x6)
                                                                                       THead (Flat Appl) x1 (THead (Bind Abbr) x5 x6)
                                                                               end of h2
                                                                               by (sn3_pr3_trans . . h1 . h2)
                                                                               we proved sn3 c (THead (Flat Appl) x1 (THead (Bind Abbr) x5 x6))
                                                                               by (eq_ind_r . . . previous . H23)
sn3 c (THead (Flat Appl) x1 x2)
sn3 c (THead (Flat Appl) x1 x2)
                                                                case or3_intro2 : H21:ex6_6 B T T T T T λb:B.λ:T.λ:T.λ:T.λ:T.λ:T.not (eq B b Abstλb:B.λy1:T.λz1:T.λ:T.λ:T.λ:T.eq T x0 (THead (Bind b) y1 z1) λb:B.λ:T.λ:T.λz2:T.λu2:T.λy2:T.eq T x2 (THead (Bind b) y2 (THead (Flat Appl) (lift (S OO u2) z2)) λ:B.λ:T.λ:T.λ:T.λu2:T.λ:T.pr2 c x u2 λ:B.λy1:T.λ:T.λ:T.λ:T.λy2:T.pr2 c y1 y2 λb:B.λ:T.λz1:T.λz2:T.λ:T.λy2:T.pr2 (CHead c (Bind b) y2) z1 z2 
                                                                   the thesis becomes sn3 c (THead (Flat Appl) x1 x2)
                                                                      we proceed by induction on H21 to prove sn3 c (THead (Flat Appl) x1 x2)
                                                                         case ex6_6_intro : x3:B x4:T x5:T x6:T x7:T x8:T H22:not (eq B x3 Abst) H23:eq T x0 (THead (Bind x3) x4 x5) H24:eq T x2 (THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)) H25:pr2 c x x7 H26:pr2 c x4 x8 H27:pr2 (CHead c (Bind x3) x8) x5 x6 
                                                                            the thesis becomes sn3 c (THead (Flat Appl) x1 x2)
                                                                               (H28
                                                                                  we proceed by induction on H24 to prove 
                                                                                     (eq
                                                                                         T
                                                                                         THead (Flat Appl) t0 (THead (Flat Appl) x x0)
                                                                                         THead
                                                                                           Flat Appl
                                                                                           x1
                                                                                           THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                       P:Prop.P
                                                                                     case refl_equal : 
                                                                                        the thesis becomes the hypothesis H19

                                                                                     (eq
                                                                                         T
                                                                                         THead (Flat Appl) t0 (THead (Flat Appl) x x0)
                                                                                         THead
                                                                                           Flat Appl
                                                                                           x1
                                                                                           THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                       P:Prop.P
                                                                               end of H28
                                                                               (H32
                                                                                  we proceed by induction on H23 to prove 
                                                                                     u2:T
                                                                                       .pr3 c (THead (Flat Appl) x (THead (Bind x3) x4 x5)) u2
                                                                                         ((iso (THead (Flat Appl) x (THead (Bind x3) x4 x5)) u2)P:Prop.P
                                                                                              sn3 c (THead (Flat Appl) t0 u2))
                                                                                     case refl_equal : 
                                                                                        the thesis becomes the hypothesis H8

                                                                                     u2:T
                                                                                       .pr3 c (THead (Flat Appl) x (THead (Bind x3) x4 x5)) u2
                                                                                         ((iso (THead (Flat Appl) x (THead (Bind x3) x4 x5)) u2)P:Prop.P
                                                                                              sn3 c (THead (Flat Appl) t0 u2))
                                                                               end of H32
                                                                               (h1
                                                                                  (h1
                                                                                     (h1
                                                                                        (h1by (pr0_refl .) we proved pr0 x x
                                                                                        (h2by (pr0_refl .) we proved pr0 x4 x4
                                                                                        (h3by (pr0_refl .) we proved pr0 x5 x5
                                                                                        by (pr0_upsilon . H22 . . h1 . . h2 . . h3)
                                                                                        we proved 
                                                                                           pr0
                                                                                             THead (Flat Appl) x (THead (Bind x3) x4 x5)
                                                                                             THead (Bind x3) x4 (THead (Flat Appl) (lift (S OO x) x5)
                                                                                        by (pr2_free . . . previous)

                                                                                           pr2
                                                                                             c
                                                                                             THead (Flat Appl) x (THead (Bind x3) x4 x5)
                                                                                             THead (Bind x3) x4 (THead (Flat Appl) (lift (S OO x) x5)
                                                                                     end of h1
                                                                                     (h2
                                                                                        (h1by (pr3_pr2 . . . H26) we proved pr3 c x4 x8
                                                                                        (h2
                                                                                           (h1
                                                                                              (h1
                                                                                                 by (drop_refl .)
                                                                                                 we proved drop O O c c
                                                                                                 that is equivalent to drop (r (Bind x3) OO c c
                                                                                                 by (drop_drop . . . . previous .)
drop (S OO (CHead c (Bind x3) x8) c
                                                                                              end of h1
                                                                                              (h2by (pr3_pr2 . . . H25) we proved pr3 c x x7
                                                                                              by (pr3_lift . . . . h1 . . h2)
pr3 (CHead c (Bind x3) x8) (lift (S OO x) (lift (S OO x7)
                                                                                           end of h1
                                                                                           (h2
                                                                                              by (pr2_cflat . . . H27 . .)
                                                                                              we proved pr2 (CHead (CHead c (Bind x3) x8) (Flat Appl) (lift (S OO x7)) x5 x6
                                                                                              by (pr3_pr2 . . . previous)
pr3 (CHead (CHead c (Bind x3) x8) (Flat Appl) (lift (S OO x7)) x5 x6
                                                                                           end of h2
                                                                                           by (pr3_head_12 . . . h1 . . . h2)

                                                                                              pr3
                                                                                                CHead c (Bind x3) x8
                                                                                                THead (Flat Appl) (lift (S OO x) x5
                                                                                                THead (Flat Appl) (lift (S OO x7) x6
                                                                                        end of h2
                                                                                        by (pr3_head_12 . . . h1 . . . h2)

                                                                                           pr3
                                                                                             c
                                                                                             THead (Bind x3) x4 (THead (Flat Appl) (lift (S OO x) x5)
                                                                                             THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                                     end of h2
                                                                                     by (pr3_sing . . . h1 . h2)

                                                                                        pr3
                                                                                          c
                                                                                          THead (Flat Appl) x (THead (Bind x3) x4 x5)
                                                                                          THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                                  end of h1
                                                                                  (h2
                                                                                      suppose H34
                                                                                         iso
                                                                                           THead (Flat Appl) x (THead (Bind x3) x4 x5)
                                                                                           THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                                      assume PProp
                                                                                        (H35
                                                                                           by cases on H34 we prove 
                                                                                              (eq
                                                                                                  T
                                                                                                  THead (Flat Appl) x (THead (Bind x3) x4 x5)
                                                                                                  THead (Flat Appl) x (THead (Bind x3) x4 x5))
                                                                                                ((eq
                                                                                                       T
                                                                                                       THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                                                       THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                                     P)
                                                                                              case iso_sort n1:nat n2:nat 
                                                                                                 the thesis becomes 
                                                                                                       H35:eq T (TSort n1) (THead (Flat Appl) x (THead (Bind x3) x4 x5))
                                                                                                         .H36:eq
                                                                                                                      T
                                                                                                                      TSort n2
                                                                                                                      THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                                                           .P
                                                                                                  suppose H35eq T (TSort n1) (THead (Flat Appl) x (THead (Bind x3) x4 x5))
                                                                                                  suppose H36
                                                                                                     eq
                                                                                                       T
                                                                                                       TSort n2
                                                                                                       THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                                                    (H37
                                                                                                       we proceed by induction on H35 to prove 
                                                                                                          <λ:T.Prop>
                                                                                                            CASE THead (Flat Appl) x (THead (Bind x3) x4 x5) OF
                                                                                                              TSort True
                                                                                                            | TLRef False
                                                                                                            | THead   False
                                                                                                          case refl_equal : 
                                                                                                             the thesis becomes 
                                                                                                             <λ:T.Prop>
                                                                                                               CASE TSort n1 OF
                                                                                                                 TSort True
                                                                                                               | TLRef False
                                                                                                               | THead   False
                                                                                                                consider I
                                                                                                                we proved True

                                                                                                                   <λ:T.Prop>
                                                                                                                     CASE TSort n1 OF
                                                                                                                       TSort True
                                                                                                                     | TLRef False
                                                                                                                     | THead   False

                                                                                                          <λ:T.Prop>
                                                                                                            CASE THead (Flat Appl) x (THead (Bind x3) x4 x5) OF
                                                                                                              TSort True
                                                                                                            | TLRef False
                                                                                                            | THead   False
                                                                                                    end of H37
                                                                                                    consider H37
                                                                                                    we proved 
                                                                                                       <λ:T.Prop>
                                                                                                         CASE THead (Flat Appl) x (THead (Bind x3) x4 x5) OF
                                                                                                           TSort True
                                                                                                         | TLRef False
                                                                                                         | THead   False
                                                                                                    that is equivalent to False
                                                                                                    we proceed by induction on the previous result to prove 
                                                                                                       (eq
                                                                                                           T
                                                                                                           TSort n2
                                                                                                           THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                                         P
                                                                                                    we proved 
                                                                                                       (eq
                                                                                                           T
                                                                                                           TSort n2
                                                                                                           THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                                         P
                                                                                                    by (previous H36)
                                                                                                    we proved P

                                                                                                    H35:eq T (TSort n1) (THead (Flat Appl) x (THead (Bind x3) x4 x5))
                                                                                                      .H36:eq
                                                                                                                   T
                                                                                                                   TSort n2
                                                                                                                   THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                                                        .P
                                                                                              case iso_lref i1:nat i2:nat 
                                                                                                 the thesis becomes 
                                                                                                       H35:eq T (TLRef i1) (THead (Flat Appl) x (THead (Bind x3) x4 x5))
                                                                                                         .H36:eq
                                                                                                                      T
                                                                                                                      TLRef i2
                                                                                                                      THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                                                           .P
                                                                                                  suppose H35eq T (TLRef i1) (THead (Flat Appl) x (THead (Bind x3) x4 x5))
                                                                                                  suppose H36
                                                                                                     eq
                                                                                                       T
                                                                                                       TLRef i2
                                                                                                       THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                                                    (H37
                                                                                                       we proceed by induction on H35 to prove 
                                                                                                          <λ:T.Prop>
                                                                                                            CASE THead (Flat Appl) x (THead (Bind x3) x4 x5) OF
                                                                                                              TSort False
                                                                                                            | TLRef True
                                                                                                            | THead   False
                                                                                                          case refl_equal : 
                                                                                                             the thesis becomes 
                                                                                                             <λ:T.Prop>
                                                                                                               CASE TLRef i1 OF
                                                                                                                 TSort False
                                                                                                               | TLRef True
                                                                                                               | THead   False
                                                                                                                consider I
                                                                                                                we proved True

                                                                                                                   <λ:T.Prop>
                                                                                                                     CASE TLRef i1 OF
                                                                                                                       TSort False
                                                                                                                     | TLRef True
                                                                                                                     | THead   False

                                                                                                          <λ:T.Prop>
                                                                                                            CASE THead (Flat Appl) x (THead (Bind x3) x4 x5) OF
                                                                                                              TSort False
                                                                                                            | TLRef True
                                                                                                            | THead   False
                                                                                                    end of H37
                                                                                                    consider H37
                                                                                                    we proved 
                                                                                                       <λ:T.Prop>
                                                                                                         CASE THead (Flat Appl) x (THead (Bind x3) x4 x5) OF
                                                                                                           TSort False
                                                                                                         | TLRef True
                                                                                                         | THead   False
                                                                                                    that is equivalent to False
                                                                                                    we proceed by induction on the previous result to prove 
                                                                                                       (eq
                                                                                                           T
                                                                                                           TLRef i2
                                                                                                           THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                                         P
                                                                                                    we proved 
                                                                                                       (eq
                                                                                                           T
                                                                                                           TLRef i2
                                                                                                           THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                                         P
                                                                                                    by (previous H36)
                                                                                                    we proved P

                                                                                                    H35:eq T (TLRef i1) (THead (Flat Appl) x (THead (Bind x3) x4 x5))
                                                                                                      .H36:eq
                                                                                                                   T
                                                                                                                   TLRef i2
                                                                                                                   THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                                                        .P
                                                                                              case iso_head v4:T v5:T t4:T t5:T k:K 
                                                                                                 the thesis becomes 
                                                                                                       H35:eq T (THead k v4 t4) (THead (Flat Appl) x (THead (Bind x3) x4 x5))
                                                                                                         .H36:eq
                                                                                                                      T
                                                                                                                      THead k v5 t5
                                                                                                                      THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                                                           .P
                                                                                                  suppose H35eq T (THead k v4 t4) (THead (Flat Appl) x (THead (Bind x3) x4 x5))
                                                                                                  suppose H36
                                                                                                     eq
                                                                                                       T
                                                                                                       THead k v5 t5
                                                                                                       THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                                                    (H37
                                                                                                       by (f_equal . . . . . H35)
                                                                                                       we proved 
                                                                                                          eq
                                                                                                            T
                                                                                                            <λ:T.T> CASE THead k v4 t4 OF TSort t4 | TLRef t4 | THead   tt
                                                                                                            <λ:T.T>
                                                                                                              CASE THead (Flat Appl) x (THead (Bind x3) x4 x5) OF
                                                                                                                TSort t4
                                                                                                              | TLRef t4
                                                                                                              | THead   tt

                                                                                                          eq
                                                                                                            T
                                                                                                            λe:T.<λ:T.T> CASE e OF TSort t4 | TLRef t4 | THead   tt (THead k v4 t4)
                                                                                                            λe:T.<λ:T.T> CASE e OF TSort t4 | TLRef t4 | THead   tt
                                                                                                              THead (Flat Appl) x (THead (Bind x3) x4 x5)
                                                                                                    end of H37
                                                                                                    (h1
                                                                                                       (H38
                                                                                                          by (f_equal . . . . . H35)
                                                                                                          we proved 
                                                                                                             eq
                                                                                                               T
                                                                                                               <λ:T.T> CASE THead k v4 t4 OF TSort v4 | TLRef v4 | THead  t t
                                                                                                               <λ:T.T>
                                                                                                                 CASE THead (Flat Appl) x (THead (Bind x3) x4 x5) OF
                                                                                                                   TSort v4
                                                                                                                 | TLRef v4
                                                                                                                 | THead  t t

                                                                                                             eq
                                                                                                               T
                                                                                                               λe:T.<λ:T.T> CASE e OF TSort v4 | TLRef v4 | THead  t t (THead k v4 t4)
                                                                                                               λe:T.<λ:T.T> CASE e OF TSort v4 | TLRef v4 | THead  t t
                                                                                                                 THead (Flat Appl) x (THead (Bind x3) x4 x5)
                                                                                                       end of H38
                                                                                                       (h1
                                                                                                          (H39
                                                                                                             by (f_equal . . . . . H35)
                                                                                                             we proved 
                                                                                                                eq
                                                                                                                  K
                                                                                                                  <λ:T.K> CASE THead k v4 t4 OF TSort k | TLRef k | THead k0  k0
                                                                                                                  <λ:T.K>
                                                                                                                    CASE THead (Flat Appl) x (THead (Bind x3) x4 x5) OF
                                                                                                                      TSort k
                                                                                                                    | TLRef k
                                                                                                                    | THead k0  k0

                                                                                                                eq
                                                                                                                  K
                                                                                                                  λe:T.<λ:T.K> CASE e OF TSort k | TLRef k | THead k0  k0 (THead k v4 t4)
                                                                                                                  λe:T.<λ:T.K> CASE e OF TSort k | TLRef k | THead k0  k0
                                                                                                                    THead (Flat Appl) x (THead (Bind x3) x4 x5)
                                                                                                          end of H39
                                                                                                          consider H39
                                                                                                          we proved 
                                                                                                             eq
                                                                                                               K
                                                                                                               <λ:T.K> CASE THead k v4 t4 OF TSort k | TLRef k | THead k0  k0
                                                                                                               <λ:T.K>
                                                                                                                 CASE THead (Flat Appl) x (THead (Bind x3) x4 x5) OF
                                                                                                                   TSort k
                                                                                                                 | TLRef k
                                                                                                                 | THead k0  k0
                                                                                                          that is equivalent to eq K k (Flat Appl)
                                                                                                          by (sym_eq . . . previous)
                                                                                                          we proved eq K (Flat Appl) k
                                                                                                          we proceed by induction on the previous result to prove 
                                                                                                             eq T v4 x
                                                                                                               (eq T t4 (THead (Bind x3) x4 x5)
                                                                                                                    ((eq
                                                                                                                           T
                                                                                                                           THead k v5 t5
                                                                                                                           THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                                                         P))
                                                                                                             case refl_equal : 
                                                                                                                the thesis becomes 
                                                                                                                eq T v4 x
                                                                                                                  (eq T t4 (THead (Bind x3) x4 x5)
                                                                                                                       ((eq
                                                                                                                              T
                                                                                                                              THead (Flat Appl) v5 t5
                                                                                                                              THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                                                            P))
                                                                                                                   suppose H40eq T v4 x
                                                                                                                      by (sym_eq . . . H40)
                                                                                                                      we proved eq T x v4
                                                                                                                      we proceed by induction on the previous result to prove 
                                                                                                                         eq T t4 (THead (Bind x3) x4 x5)
                                                                                                                           ((eq
                                                                                                                                  T
                                                                                                                                  THead (Flat Appl) v5 t5
                                                                                                                                  THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                                                                P)
                                                                                                                         case refl_equal : 
                                                                                                                            the thesis becomes 
                                                                                                                            eq T t4 (THead (Bind x3) x4 x5)
                                                                                                                              ((eq
                                                                                                                                     T
                                                                                                                                     THead (Flat Appl) v5 t5
                                                                                                                                     THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                                                                   P)
                                                                                                                               suppose H41eq T t4 (THead (Bind x3) x4 x5)
                                                                                                                                  by (sym_eq . . . H41)
                                                                                                                                  we proved eq T (THead (Bind x3) x4 x5) t4
                                                                                                                                  we proceed by induction on the previous result to prove 
                                                                                                                                     (eq
                                                                                                                                         T
                                                                                                                                         THead (Flat Appl) v5 t5
                                                                                                                                         THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                                                                       P
                                                                                                                                     case refl_equal : 
                                                                                                                                        the thesis becomes 
                                                                                                                                        (eq
                                                                                                                                            T
                                                                                                                                            THead (Flat Appl) v5 t5
                                                                                                                                            THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                                                                          P
                                                                                                                                           suppose H42
                                                                                                                                              eq
                                                                                                                                                T
                                                                                                                                                THead (Flat Appl) v5 t5
                                                                                                                                                THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                                                                                              (H43
                                                                                                                                                 we proceed by induction on H42 to prove 
                                                                                                                                                    <λ:T.Prop>
                                                                                                                                                      CASE THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6) OF
                                                                                                                                                        TSort False
                                                                                                                                                      | TLRef False
                                                                                                                                                      | THead k0  <λ:K.Prop> CASE k0 OF Bind False | Flat True
                                                                                                                                                    case refl_equal : 
                                                                                                                                                       the thesis becomes 
                                                                                                                                                       <λ:T.Prop>
                                                                                                                                                         CASE THead (Flat Appl) v5 t5 OF
                                                                                                                                                           TSort False
                                                                                                                                                         | TLRef False
                                                                                                                                                         | THead k0  <λ:K.Prop> CASE k0 OF Bind False | Flat True
                                                                                                                                                          consider I
                                                                                                                                                          we proved True

                                                                                                                                                             <λ:T.Prop>
                                                                                                                                                               CASE THead (Flat Appl) v5 t5 OF
                                                                                                                                                                 TSort False
                                                                                                                                                               | TLRef False
                                                                                                                                                               | THead k0  <λ:K.Prop> CASE k0 OF Bind False | Flat True

                                                                                                                                                    <λ:T.Prop>
                                                                                                                                                      CASE THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6) OF
                                                                                                                                                        TSort False
                                                                                                                                                      | TLRef False
                                                                                                                                                      | THead k0  <λ:K.Prop> CASE k0 OF Bind False | Flat True
                                                                                                                                              end of H43
                                                                                                                                              consider H43
                                                                                                                                              we proved 
                                                                                                                                                 <λ:T.Prop>
                                                                                                                                                   CASE THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6) OF
                                                                                                                                                     TSort False
                                                                                                                                                   | TLRef False
                                                                                                                                                   | THead k0  <λ:K.Prop> CASE k0 OF Bind False | Flat True
                                                                                                                                              that is equivalent to False
                                                                                                                                              we proceed by induction on the previous result to prove P
                                                                                                                                              we proved P

                                                                                                                                              (eq
                                                                                                                                                  T
                                                                                                                                                  THead (Flat Appl) v5 t5
                                                                                                                                                  THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                                                                                P
                                                                                                                                  we proved 
                                                                                                                                     (eq
                                                                                                                                         T
                                                                                                                                         THead (Flat Appl) v5 t5
                                                                                                                                         THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                                                                       P

                                                                                                                                  eq T t4 (THead (Bind x3) x4 x5)
                                                                                                                                    ((eq
                                                                                                                                           T
                                                                                                                                           THead (Flat Appl) v5 t5
                                                                                                                                           THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                                                                         P)
                                                                                                                      we proved 
                                                                                                                         eq T t4 (THead (Bind x3) x4 x5)
                                                                                                                           ((eq
                                                                                                                                  T
                                                                                                                                  THead (Flat Appl) v5 t5
                                                                                                                                  THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                                                                P)

                                                                                                                      eq T v4 x
                                                                                                                        (eq T t4 (THead (Bind x3) x4 x5)
                                                                                                                             ((eq
                                                                                                                                    T
                                                                                                                                    THead (Flat Appl) v5 t5
                                                                                                                                    THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                                                                  P))

                                                                                                             eq T v4 x
                                                                                                               (eq T t4 (THead (Bind x3) x4 x5)
                                                                                                                    ((eq
                                                                                                                           T
                                                                                                                           THead k v5 t5
                                                                                                                           THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                                                         P))
                                                                                                       end of h1
                                                                                                       (h2
                                                                                                          consider H38
                                                                                                          we proved 
                                                                                                             eq
                                                                                                               T
                                                                                                               <λ:T.T> CASE THead k v4 t4 OF TSort v4 | TLRef v4 | THead  t t
                                                                                                               <λ:T.T>
                                                                                                                 CASE THead (Flat Appl) x (THead (Bind x3) x4 x5) OF
                                                                                                                   TSort v4
                                                                                                                 | TLRef v4
                                                                                                                 | THead  t t
eq T v4 x
                                                                                                       end of h2
                                                                                                       by (h1 h2)

                                                                                                          eq T t4 (THead (Bind x3) x4 x5)
                                                                                                            ((eq
                                                                                                                   T
                                                                                                                   THead k v5 t5
                                                                                                                   THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                                                 P)
                                                                                                    end of h1
                                                                                                    (h2
                                                                                                       consider H37
                                                                                                       we proved 
                                                                                                          eq
                                                                                                            T
                                                                                                            <λ:T.T> CASE THead k v4 t4 OF TSort t4 | TLRef t4 | THead   tt
                                                                                                            <λ:T.T>
                                                                                                              CASE THead (Flat Appl) x (THead (Bind x3) x4 x5) OF
                                                                                                                TSort t4
                                                                                                              | TLRef t4
                                                                                                              | THead   tt
eq T t4 (THead (Bind x3) x4 x5)
                                                                                                    end of h2
                                                                                                    by (h1 h2)
                                                                                                    we proved 
                                                                                                       (eq
                                                                                                           T
                                                                                                           THead k v5 t5
                                                                                                           THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                                         P
                                                                                                    by (previous H36)
                                                                                                    we proved P

                                                                                                    H35:eq T (THead k v4 t4) (THead (Flat Appl) x (THead (Bind x3) x4 x5))
                                                                                                      .H36:eq
                                                                                                                   T
                                                                                                                   THead k v5 t5
                                                                                                                   THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                                                        .P

                                                                                              (eq
                                                                                                  T
                                                                                                  THead (Flat Appl) x (THead (Bind x3) x4 x5)
                                                                                                  THead (Flat Appl) x (THead (Bind x3) x4 x5))
                                                                                                ((eq
                                                                                                       T
                                                                                                       THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                                                       THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                                     P)
                                                                                        end of H35
                                                                                        (h1
                                                                                           by (refl_equal . .)

                                                                                              eq
                                                                                                T
                                                                                                THead (Flat Appl) x (THead (Bind x3) x4 x5)
                                                                                                THead (Flat Appl) x (THead (Bind x3) x4 x5)
                                                                                        end of h1
                                                                                        (h2
                                                                                           by (refl_equal . .)

                                                                                              eq
                                                                                                T
                                                                                                THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                                                THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                                        end of h2
                                                                                        by (H35 h1 h2)
                                                                                        we proved P

                                                                                        (iso
                                                                                            THead (Flat Appl) x (THead (Bind x3) x4 x5)
                                                                                            THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6))
                                                                                          P:Prop.P
                                                                                  end of h2
                                                                                  by (H32 . h1 h2)

                                                                                     sn3
                                                                                       c
                                                                                       THead
                                                                                         Flat Appl
                                                                                         t0
                                                                                         THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                               end of h1
                                                                               (h2
                                                                                  by (pr2_head_1 . . . H17 . .)
                                                                                  we proved 
                                                                                     pr2
                                                                                       c
                                                                                       THead
                                                                                         Flat Appl
                                                                                         t0
                                                                                         THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                                       THead
                                                                                         Flat Appl
                                                                                         x1
                                                                                         THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                                  by (pr3_pr2 . . . previous)

                                                                                     pr3
                                                                                       c
                                                                                       THead
                                                                                         Flat Appl
                                                                                         t0
                                                                                         THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                                       THead
                                                                                         Flat Appl
                                                                                         x1
                                                                                         THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                               end of h2
                                                                               by (sn3_pr3_trans . . h1 . h2)
                                                                               we proved 
                                                                                  sn3
                                                                                    c
                                                                                    THead
                                                                                      Flat Appl
                                                                                      x1
                                                                                      THead (Bind x3) x8 (THead (Flat Appl) (lift (S OO x7) x6)
                                                                               by (eq_ind_r . . . previous . H24)
sn3 c (THead (Flat Appl) x1 x2)
sn3 c (THead (Flat Appl) x1 x2)
                                                             we proved sn3 c (THead (Flat Appl) x1 x2)
                                                             by (eq_ind_r . . . previous . H16)
sn3 c t3
sn3 c t3
                                              case or3_intro1 : H15:ex4_4 T T T T λy1:T.λz1:T.λ:T.λ:T.eq T (THead (Flat Appl) x x0) (THead (Bind Abst) y1 z1) λ:T.λ:T.λu2:T.λt4:T.eq T t3 (THead (Bind Abbr) u2 t4) λ:T.λ:T.λu2:T.λ:T.pr2 c t0 u2 λ:T.λz1:T.λ:T.λt4:T.b:B.u:T.(pr2 (CHead c (Bind b) u) z1 t4) 
                                                 the thesis becomes sn3 c t3
                                                    we proceed by induction on H15 to prove sn3 c t3
                                                       case ex4_4_intro : x1:T x2:T x3:T x4:T H16:eq T (THead (Flat Appl) x x0) (THead (Bind Abst) x1 x2) H17:eq T t3 (THead (Bind Abbr) x3 x4) :pr2 c t0 x3 :b:B.u:T.(pr2 (CHead c (Bind b) u) x2 x4) 
                                                          the thesis becomes sn3 c t3
                                                             (H21
                                                                we proceed by induction on H16 to prove 
                                                                   <λ:T.Prop>
                                                                     CASE THead (Bind Abst) x1 x2 OF
                                                                       TSort False
                                                                     | TLRef False
                                                                     | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True
                                                                   case refl_equal : 
                                                                      the thesis becomes 
                                                                      <λ:T.Prop>
                                                                        CASE THead (Flat Appl) x x0 OF
                                                                          TSort False
                                                                        | TLRef False
                                                                        | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True
                                                                         consider I
                                                                         we proved True

                                                                            <λ:T.Prop>
                                                                              CASE THead (Flat Appl) x x0 OF
                                                                                TSort False
                                                                              | TLRef False
                                                                              | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True

                                                                   <λ:T.Prop>
                                                                     CASE THead (Bind Abst) x1 x2 OF
                                                                       TSort False
                                                                     | TLRef False
                                                                     | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True
                                                             end of H21
                                                             consider H21
                                                             we proved 
                                                                <λ:T.Prop>
                                                                  CASE THead (Bind Abst) x1 x2 OF
                                                                    TSort False
                                                                  | TLRef False
                                                                  | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True
                                                             that is equivalent to False
                                                             we proceed by induction on the previous result to prove sn3 c (THead (Bind Abbr) x3 x4)
                                                             we proved sn3 c (THead (Bind Abbr) x3 x4)
                                                             by (eq_ind_r . . . previous . H17)
sn3 c t3
sn3 c t3
                                              case or3_intro2 : H15:ex6_6 B T T T T T λb:B.λ:T.λ:T.λ:T.λ:T.λ:T.not (eq B b Abstλb:B.λy1:T.λz1:T.λ:T.λ:T.λ:T.eq T (THead (Flat Appl) x x0) (THead (Bind b) y1 z1) λb:B.λ:T.λ:T.λz2:T.λu2:T.λy2:T.eq T t3 (THead (Bind b) y2 (THead (Flat Appl) (lift (S OO u2) z2)) λ:B.λ:T.λ:T.λ:T.λu2:T.λ:T.pr2 c t0 u2 λ:B.λy1:T.λ:T.λ:T.λ:T.λy2:T.pr2 c y1 y2 λb:B.λ:T.λz1:T.λz2:T.λ:T.λy2:T.pr2 (CHead c (Bind b) y2) z1 z2 
                                                 the thesis becomes sn3 c t3
                                                    we proceed by induction on H15 to prove sn3 c t3
                                                       case ex6_6_intro : x1:B x2:T x3:T x4:T x5:T x6:T :not (eq B x1 Abst) H17:eq T (THead (Flat Appl) x x0) (THead (Bind x1) x2 x3) H18:eq T t3 (THead (Bind x1) x6 (THead (Flat Appl) (lift (S OO x5) x4)) :pr2 c t0 x5 :pr2 c x2 x6 :pr2 (CHead c (Bind x1) x6) x3 x4 
                                                          the thesis becomes sn3 c t3
                                                             (H23
                                                                we proceed by induction on H17 to prove 
                                                                   <λ:T.Prop>
                                                                     CASE THead (Bind x1) x2 x3 OF
                                                                       TSort False
                                                                     | TLRef False
                                                                     | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True
                                                                   case refl_equal : 
                                                                      the thesis becomes 
                                                                      <λ:T.Prop>
                                                                        CASE THead (Flat Appl) x x0 OF
                                                                          TSort False
                                                                        | TLRef False
                                                                        | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True
                                                                         consider I
                                                                         we proved True

                                                                            <λ:T.Prop>
                                                                              CASE THead (Flat Appl) x x0 OF
                                                                                TSort False
                                                                              | TLRef False
                                                                              | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True

                                                                   <λ:T.Prop>
                                                                     CASE THead (Bind x1) x2 x3 OF
                                                                       TSort False
                                                                     | TLRef False
                                                                     | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True
                                                             end of H23
                                                             consider H23
                                                             we proved 
                                                                <λ:T.Prop>
                                                                  CASE THead (Bind x1) x2 x3 OF
                                                                    TSort False
                                                                  | TLRef False
                                                                  | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True
                                                             that is equivalent to False
                                                             we proceed by induction on the previous result to prove sn3 c (THead (Bind x1) x6 (THead (Flat Appl) (lift (S OO x5) x4))
                                                             we proved sn3 c (THead (Bind x1) x6 (THead (Flat Appl) (lift (S OO x5) x4))
                                                             by (eq_ind_r . . . previous . H18)
sn3 c t3
sn3 c t3
                                           we proved sn3 c t3
                                        we proved 
                                           t3:T
                                             .eq T (THead (Flat Appl) t0 (THead (Flat Appl) x x0)) t3
                                                 P:Prop.P
                                               (pr2 c (THead (Flat Appl) t0 (THead (Flat Appl) x x0)) t3)(sn3 c t3)
                                        by (sn3_pr2_intro . . previous)
                                        we proved sn3 c (THead (Flat Appl) t0 (THead (Flat Appl) x x0))
                                        by (eq_ind_r . . . previous . H3)
                                        we proved sn3 c (THead (Flat Appl) t0 t2)

                                        H7:u2:T.(pr3 c t2 u2)((iso t2 u2)P:Prop.P)(sn3 c (THead (Flat Appl) t0 u2))
                                          .sn3 c (THead (Flat Appl) t0 t2)
                            we proved 
                               u2:T.(pr3 c t2 u2)((iso t2 u2)P:Prop.P)(sn3 c (THead (Flat Appl) v2 u2))
                                 sn3 c (THead (Flat Appl) v2 t2)

                            x:T
                              .x0:T
                                .H3:eq T t2 (THead (Flat Appl) x x0)
                                  .v2:T
                                    .H4:sn3 c v2
                                      .u2:T.(pr3 c t2 u2)((iso t2 u2)P:Prop.P)(sn3 c (THead (Flat Appl) v2 u2))
                                        sn3 c (THead (Flat Appl) v2 t2)
                we proved 
                   x:T
                     .x0:T
                       .eq T y (THead (Flat Appl) x x0)
                         v2:T
                              .sn3 c v2
                                (u2:T
                                       .pr3 c y u2
                                         ((iso y u2)P:Prop.P)(sn3 c (THead (Flat Appl) v2 u2))
                                     sn3 c (THead (Flat Appl) v2 y))
                by (unintro . . . previous)
                we proved 
                   x:T
                     .eq T y (THead (Flat Appl) v1 x)
                       v2:T
                            .sn3 c v2
                              (u2:T
                                     .pr3 c y u2
                                       ((iso y u2)P:Prop.P)(sn3 c (THead (Flat Appl) v2 u2))
                                   sn3 c (THead (Flat Appl) v2 y))
                by (unintro . . . previous)
                we proved 
                   eq T y (THead (Flat Appl) v1 t1)
                     v2:T
                          .sn3 c v2
                            (u2:T
                                   .pr3 c y u2
                                     ((iso y u2)P:Prop.P)(sn3 c (THead (Flat Appl) v2 u2))
                                 sn3 c (THead (Flat Appl) v2 y))
             we proved 
                y:T
                  .sn3 c y
                    (eq T y (THead (Flat Appl) v1 t1)
                         v2:T
                              .sn3 c v2
                                (u2:T
                                       .pr3 c y u2
                                         ((iso y u2)P:Prop.P)(sn3 c (THead (Flat Appl) v2 u2))
                                     sn3 c (THead (Flat Appl) v2 y)))
             by (insert_eq . . . . previous H)
             we proved 
                v2:T
                  .sn3 c v2
                    (u2:T
                           .pr3 c (THead (Flat Appl) v1 t1) u2
                             ((iso (THead (Flat Appl) v1 t1) u2)P:Prop.P
                                  sn3 c (THead (Flat Appl) v2 u2))
                         sn3 c (THead (Flat Appl) v2 (THead (Flat Appl) v1 t1)))
          we proved 
             c:C
               .sn3 c (THead (Flat Appl) v1 t1)
                 v2:T
                      .sn3 c v2
                        (u2:T
                               .pr3 c (THead (Flat Appl) v1 t1) u2
                                 ((iso (THead (Flat Appl) v1 t1) u2)P:Prop.P
                                      sn3 c (THead (Flat Appl) v2 u2))
                             sn3 c (THead (Flat Appl) v2 (THead (Flat Appl) v1 t1)))
          that is equivalent to 
             let u1 := THead (Flat Appl) v1 t1
             in c:C
                    .sn3 c u1
                      v2:T
                           .sn3 c v2
                             (u2:T.(pr3 c u1 u2)((iso u1 u2)P:Prop.P)(sn3 c (THead (Flat Appl) v2 u2))
                                  sn3 c (THead (Flat Appl) v2 u1))
       we proved 
          v1:T
            .t1:T
              .let u1 := THead (Flat Appl) v1 t1
              in c:C
                     .sn3 c u1
                       v2:T
                            .sn3 c v2
                              (u2:T.(pr3 c u1 u2)((iso u1 u2)P:Prop.P)(sn3 c (THead (Flat Appl) v2 u2))
                                   sn3 c (THead (Flat Appl) v2 u1))