DEFINITION pr3_pr0_pr2_t()
TYPE =
       u1:T.u2:T.(pr0 u1 u2)c:C.t1:T.t2:T.k:K.(pr2 (CHead c k u2) t1 t2)(pr3 (CHead c k u1) t1 t2)
BODY =
        assume u1T
        assume u2T
        suppose Hpr0 u1 u2
        assume cC
        assume t1T
        assume t2T
        assume kK
        suppose H0pr2 (CHead c k u2) t1 t2
           assume yC
           suppose H1pr2 y t1 t2
             we proceed by induction on H1 to prove (eq C y (CHead c k u2))(pr3 (CHead c k u1) t1 t2)
                case pr2_free : c0:C t3:T t4:T H2:pr0 t3 t4 
                   the thesis becomes (eq C c0 (CHead c k u2))(pr3 (CHead c k u1) t3 t4)
                      suppose eq C c0 (CHead c k u2)
                         by (pr2_free . . . H2)
                         we proved pr2 (CHead c k u1) t3 t4
                         by (pr3_pr2 . . . previous)
                         we proved pr3 (CHead c k u1) t3 t4
(eq C c0 (CHead c k u2))(pr3 (CHead c k u1) t3 t4)
                case pr2_delta : c0:C d:C u:T i:nat H2:getl i c0 (CHead d (Bind Abbr) u) t3:T t4:T H3:pr0 t3 t4 t:T H4:subst0 i u t4 t 
                   the thesis becomes H5:(eq C c0 (CHead c k u2)).(pr3 (CHead c k u1) t3 t)
                      suppose H5eq C c0 (CHead c k u2)
                         (H6
                            we proceed by induction on H5 to prove getl i (CHead c k u2) (CHead d (Bind Abbr) u)
                               case refl_equal : 
                                  the thesis becomes the hypothesis H2
getl i (CHead c k u2) (CHead d (Bind Abbr) u)
                         end of H6
                          suppose H7getl O (CHead c k u2) (CHead d (Bind Abbr) u)
                          suppose H8subst0 O u t4 t
                               assume bB
                               suppose H9getl O (CHead c (Bind b) u2) (CHead d (Bind Abbr) u)
                                  (H10
                                     by (getl_gen_O . . H9)
                                     we proved clear (CHead c (Bind b) u2) (CHead d (Bind Abbr) u)
                                     by (clear_gen_bind . . . . previous)
                                     we proved eq C (CHead d (Bind Abbr) u) (CHead c (Bind b) u2)
                                     by (f_equal . . . . . previous)
                                     we proved 
                                        eq
                                          C
                                          <λ:C.C> CASE CHead d (Bind Abbr) u OF CSort d | CHead c1  c1
                                          <λ:C.C> CASE CHead c (Bind b) u2 OF CSort d | CHead c1  c1

                                        eq
                                          C
                                          λe:C.<λ:C.C> CASE e OF CSort d | CHead c1  c1 (CHead d (Bind Abbr) u)
                                          λe:C.<λ:C.C> CASE e OF CSort d | CHead c1  c1 (CHead c (Bind b) u2)
                                  end of H10
                                  (h1
                                     (H11
                                        by (getl_gen_O . . H9)
                                        we proved clear (CHead c (Bind b) u2) (CHead d (Bind Abbr) u)
                                        by (clear_gen_bind . . . . previous)
                                        we proved eq C (CHead d (Bind Abbr) u) (CHead c (Bind b) u2)
                                        by (f_equal . . . . . previous)
                                        we proved 
                                           eq
                                             B
                                             <λ:C.B>
                                               CASE CHead d (Bind Abbr) u OF
                                                 CSort Abbr
                                               | CHead  k0 <λ:K.B> CASE k0 OF Bind b0b0 | Flat Abbr
                                             <λ:C.B>
                                               CASE CHead c (Bind b) u2 OF
                                                 CSort Abbr
                                               | CHead  k0 <λ:K.B> CASE k0 OF Bind b0b0 | Flat Abbr

                                           eq
                                             B
                                             λe:C
                                                 .<λ:C.B>
                                                   CASE e OF
                                                     CSort Abbr
                                                   | CHead  k0 <λ:K.B> CASE k0 OF Bind b0b0 | Flat Abbr
                                               CHead d (Bind Abbr) u
                                             λe:C
                                                 .<λ:C.B>
                                                   CASE e OF
                                                     CSort Abbr
                                                   | CHead  k0 <λ:K.B> CASE k0 OF Bind b0b0 | Flat Abbr
                                               CHead c (Bind b) u2
                                     end of H11
                                     (h1
                                        (H12
                                           by (getl_gen_O . . H9)
                                           we proved clear (CHead c (Bind b) u2) (CHead d (Bind Abbr) u)
                                           by (clear_gen_bind . . . . previous)
                                           we proved eq C (CHead d (Bind Abbr) u) (CHead c (Bind b) u2)
                                           by (f_equal . . . . . previous)
                                           we proved 
                                              eq
                                                T
                                                <λ:C.T> CASE CHead d (Bind Abbr) u OF CSort u | CHead   t0t0
                                                <λ:C.T> CASE CHead c (Bind b) u2 OF CSort u | CHead   t0t0

                                              eq
                                                T
                                                λe:C.<λ:C.T> CASE e OF CSort u | CHead   t0t0 (CHead d (Bind Abbr) u)
                                                λe:C.<λ:C.T> CASE e OF CSort u | CHead   t0t0 (CHead c (Bind b) u2)
                                        end of H12
                                         suppose H13eq B Abbr b
                                         suppose eq C d c
                                           (H15
                                              consider H12
                                              we proved 
                                                 eq
                                                   T
                                                   <λ:C.T> CASE CHead d (Bind Abbr) u OF CSort u | CHead   t0t0
                                                   <λ:C.T> CASE CHead c (Bind b) u2 OF CSort u | CHead   t0t0
                                              that is equivalent to eq T u u2
                                              we proceed by induction on the previous result to prove subst0 O u2 t4 t
                                                 case refl_equal : 
                                                    the thesis becomes the hypothesis H8
subst0 O u2 t4 t
                                           end of H15
                                           we proceed by induction on H13 to prove pr3 (CHead c (Bind b) u1) t3 t
                                              case refl_equal : 
                                                 the thesis becomes pr3 (CHead c (Bind Abbr) u1) t3 t
                                                    by (pr0_subst0_back . . . . H15 . H)
                                                    we proved ex2 T λt:T.subst0 O u1 t4 t λt:T.pr0 t t
                                                    we proceed by induction on the previous result to prove pr3 (CHead c (Bind Abbr) u1) t3 t
                                                       case ex_intro2 : x:T H16:subst0 O u1 t4 x H17:pr0 x t 
                                                          the thesis becomes pr3 (CHead c (Bind Abbr) u1) t3 t
                                                             (h1
                                                                by (getl_refl . . .)
                                                                we proved getl O (CHead c (Bind Abbr) u1) (CHead c (Bind Abbr) u1)
                                                                by (pr2_delta . . . . previous . . H3 . H16)
pr2 (CHead c (Bind Abbr) u1) t3 x
                                                             end of h1
                                                             (h2
                                                                by (pr2_free . . . H17)
                                                                we proved pr2 (CHead c (Bind Abbr) u1) x t
                                                                by (pr3_pr2 . . . previous)
pr3 (CHead c (Bind Abbr) u1) x t
                                                             end of h2
                                                             by (pr3_sing . . . h1 . h2)
pr3 (CHead c (Bind Abbr) u1) t3 t
pr3 (CHead c (Bind Abbr) u1) t3 t
                                           we proved pr3 (CHead c (Bind b) u1) t3 t
(eq B Abbr b)(eq C d c)(pr3 (CHead c (Bind b) u1) t3 t)
                                     end of h1
                                     (h2
                                        consider H11
                                        we proved 
                                           eq
                                             B
                                             <λ:C.B>
                                               CASE CHead d (Bind Abbr) u OF
                                                 CSort Abbr
                                               | CHead  k0 <λ:K.B> CASE k0 OF Bind b0b0 | Flat Abbr
                                             <λ:C.B>
                                               CASE CHead c (Bind b) u2 OF
                                                 CSort Abbr
                                               | CHead  k0 <λ:K.B> CASE k0 OF Bind b0b0 | Flat Abbr
eq B Abbr b
                                     end of h2
                                     by (h1 h2)
(eq C d c)(pr3 (CHead c (Bind b) u1) t3 t)
                                  end of h1
                                  (h2
                                     consider H10
                                     we proved 
                                        eq
                                          C
                                          <λ:C.C> CASE CHead d (Bind Abbr) u OF CSort d | CHead c1  c1
                                          <λ:C.C> CASE CHead c (Bind b) u2 OF CSort d | CHead c1  c1
eq C d c
                                  end of h2
                                  by (h1 h2)
                                  we proved pr3 (CHead c (Bind b) u1) t3 t

                                  H9:getl O (CHead c (Bind b) u2) (CHead d (Bind Abbr) u)
                                    .pr3 (CHead c (Bind b) u1) t3 t
                               assume fF
                               suppose H9getl O (CHead c (Flat f) u2) (CHead d (Bind Abbr) u)
                                  (h1
                                     by (drop_refl .)
drop O O c c
                                  end of h1
                                  (h2
                                     by (getl_gen_O . . H9)
                                     we proved clear (CHead c (Flat f) u2) (CHead d (Bind Abbr) u)
                                     by (clear_gen_flat . . . . previous)
clear c (CHead d (Bind Abbr) u)
                                  end of h2
                                  by (getl_intro . . . . h1 h2)
                                  we proved getl O c (CHead d (Bind Abbr) u)
                                  by (pr2_delta . . . . previous . . H3 . H8)
                                  we proved pr2 c t3 t
                                  by (pr2_cflat . . . previous . .)
                                  we proved pr2 (CHead c (Flat f) u1) t3 t
                                  by (pr3_pr2 . . . previous)
                                  we proved pr3 (CHead c (Flat f) u1) t3 t

                                  H9:getl O (CHead c (Flat f) u2) (CHead d (Bind Abbr) u)
                                    .pr3 (CHead c (Flat f) u1) t3 t
                            by (previous . H7)
                            we proved pr3 (CHead c k u1) t3 t

                            getl O (CHead c k u2) (CHead d (Bind Abbr) u)
                              (subst0 O u t4 t)(pr3 (CHead c k u1) t3 t)
                          assume i0nat
                             suppose IHi
                                getl i0 (CHead c k u2) (CHead d (Bind Abbr) u)
                                  (subst0 i0 u t4 t)(pr3 (CHead c k u1) t3 t)
                             suppose H7getl (S i0) (CHead c k u2) (CHead d (Bind Abbr) u)
                             suppose H8subst0 (S i0) u t4 t
                                  assume bB
                                   suppose H9getl (S i0) (CHead c (Bind b) u2) (CHead d (Bind Abbr) u)
                                   suppose 
                                      getl i0 (CHead c (Bind b) u2) (CHead d (Bind Abbr) u)
                                        (subst0 i0 u t4 t)(pr3 (CHead c (Bind b) u1) t3 t)
                                     by (getl_gen_S . . . . . H9)
                                     we proved getl (r (Bind b) i0) c (CHead d (Bind Abbr) u)
                                     by (getl_head . . . . previous .)
                                     we proved getl (S i0) (CHead c (Bind b) u1) (CHead d (Bind Abbr) u)
                                     by (pr2_delta . . . . previous . . H3 . H8)
                                     we proved pr2 (CHead c (Bind b) u1) t3 t
                                     by (pr3_pr2 . . . previous)
                                     we proved pr3 (CHead c (Bind b) u1) t3 t

                                     H9:getl (S i0) (CHead c (Bind b) u2) (CHead d (Bind Abbr) u)
                                       .getl i0 (CHead c (Bind b) u2) (CHead d (Bind Abbr) u)
                                           (subst0 i0 u t4 t)(pr3 (CHead c (Bind b) u1) t3 t)
                                         pr3 (CHead c (Bind b) u1) t3 t
                                  assume fF
                                   suppose H9getl (S i0) (CHead c (Flat f) u2) (CHead d (Bind Abbr) u)
                                   suppose 
                                      getl i0 (CHead c (Flat f) u2) (CHead d (Bind Abbr) u)
                                        (subst0 i0 u t4 t)(pr3 (CHead c (Flat f) u1) t3 t)
                                     (h1
                                        by (getl_gen_S . . . . . H9)
getl (r (Flat f) i0) c (CHead d (Bind Abbr) u)
                                     end of h1
                                     (h2
                                        consider H8
                                        we proved subst0 (S i0) u t4 t
subst0 (r (Flat f) i0) u t4 t
                                     end of h2
                                     by (pr2_delta . . . . h1 . . H3 . h2)
                                     we proved pr2 c t3 t
                                     by (pr2_cflat . . . previous . .)
                                     we proved pr2 (CHead c (Flat f) u1) t3 t
                                     by (pr3_pr2 . . . previous)
                                     we proved pr3 (CHead c (Flat f) u1) t3 t

                                     H9:getl (S i0) (CHead c (Flat f) u2) (CHead d (Bind Abbr) u)
                                       .getl i0 (CHead c (Flat f) u2) (CHead d (Bind Abbr) u)
                                           (subst0 i0 u t4 t)(pr3 (CHead c (Flat f) u1) t3 t)
                                         pr3 (CHead c (Flat f) u1) t3 t
                               by (previous . H7 IHi)
                               we proved pr3 (CHead c k u1) t3 t

                               H7:getl (S i0) (CHead c k u2) (CHead d (Bind Abbr) u)
                                 .H8:(subst0 (S i0) u t4 t).(pr3 (CHead c k u1) t3 t)
                         by (previous . H6 H4)
                         we proved pr3 (CHead c k u1) t3 t
H5:(eq C c0 (CHead c k u2)).(pr3 (CHead c k u1) t3 t)
             we proved (eq C y (CHead c k u2))(pr3 (CHead c k u1) t1 t2)
          we proved y:C.(pr2 y t1 t2)(eq C y (CHead c k u2))(pr3 (CHead c k u1) t1 t2)
          by (insert_eq . . . . previous H0)
          we proved pr3 (CHead c k u1) t1 t2
       we proved u1:T.u2:T.(pr0 u1 u2)c:C.t1:T.t2:T.k:K.(pr2 (CHead c k u2) t1 t2)(pr3 (CHead c k u1) t1 t2)