DEFINITION wcpr0_drop_back()
TYPE =
       ∀c1:C
         .∀c2:C
           .wcpr0 c2 c1
             →∀h:nat
                  .∀e1:C
                    .∀u1:T
                      .∀k:K
                        .drop h O c1 (CHead e1 k u1)
                          →ex3_2 C T λe2:C.λu2:T.drop h O c2 (CHead e2 k u2) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu2:T.pr0 u2 u1
BODY =
        assume c1: C
        assume c2: C
        suppose H: wcpr0 c2 c1
          we proceed by induction on H to prove 
             ∀h:nat
               .∀e1:C
                 .∀u1:T
                   .∀k:K
                     .drop h O c1 (CHead e1 k u1)
                       →ex3_2 C T λe2:C.λu2:T.drop h O c2 (CHead e2 k u2) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu2:T.pr0 u2 u1
             case wcpr0_refl : c:C ⇒
                the thesis becomes 
                ∀h:nat
                  .∀e1:C
                    .∀u1:T
                      .∀k:K
                        .∀H0:(drop h O c (CHead e1 k u1)).(ex3_2 C T λe2:C.λu2:T.drop h O c (CHead e2 k u2) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu2:T.pr0 u2 u1)
                    assume h: nat
                    assume e1: C
                    assume u1: T
                    assume k: K
                    suppose H0: drop h O c (CHead e1 k u1)
                      (h1) by (wcpr0_refl .) we proved wcpr0 e1 e1
                      (h2) by (pr0_refl .) we proved pr0 u1 u1
                      by (ex3_2_intro . . . . . . . H0 h1 h2)
                      we proved ex3_2 C T λe2:C.λu2:T.drop h O c (CHead e2 k u2) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu2:T.pr0 u2 u1

                      ∀h:nat
                        .∀e1:C
                          .∀u1:T
                            .∀k:K
                              .∀H0:(drop h O c (CHead e1 k u1)).(ex3_2 C T λe2:C.λu2:T.drop h O c (CHead e2 k u2) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu2:T.pr0 u2 u1)
             case wcpr0_comp : c3:C c4:C H0:wcpr0 c3 c4 u1:T u2:T H2:pr0 u1 u2 k:K ⇒
                the thesis becomes 
                ∀h:nat
                  .∀e1:C
                    .∀u3:T
                      .∀k0:K
                        .drop h O (CHead c4 k u2) (CHead e1 k0 u3)
                          →ex3_2 C T λe2:C.λu4:T.drop h O (CHead c3 k u1) (CHead e2 k0 u4) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu4:T.pr0 u4 u3
                (H1) by induction hypothesis we know 
                   ∀h:nat
                     .∀e1:C
                       .∀u1:T
                         .∀k:K
                           .drop h O c4 (CHead e1 k u1)
                             →ex3_2 C T λe2:C.λu2:T.drop h O c3 (CHead e2 k u2) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu2:T.pr0 u2 u1
                   assume h: nat
                      we proceed by induction on h to prove 
                         ∀e1:C
                           .∀u3:T
                             .∀k0:K
                               .drop h O (CHead c4 k u2) (CHead e1 k0 u3)
                                 →ex3_2 C T λe2:C.λu4:T.drop h O (CHead c3 k u1) (CHead e2 k0 u4) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu4:T.pr0 u4 u3
                         case O : ⇒
                            the thesis becomes 
                            ∀e1:C
                              .∀u0:T
                                .∀k0:K
                                  .drop O O (CHead c4 k u2) (CHead e1 k0 u0)
                                    →ex3_2 C T λe2:C.λu3:T.drop O O (CHead c3 k u1) (CHead e2 k0 u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0
                                assume e1: C
                                assume u0: T
                                assume k0: K
                                suppose H3: drop O O (CHead c4 k u2) (CHead e1 k0 u0)
                                  (H4) 
                                     by (drop_gen_refl . . H3)
                                     we proved eq C (CHead c4 k u2) (CHead e1 k0 u0)
                                     by (f_equal . . . . . previous)
                                     we proved 
                                        eq
                                          C
                                          <λ:C.C> CASE CHead c4 k u2 OF CSort ⇒c4 | CHead c  ⇒c
                                          <λ:C.C> CASE CHead e1 k0 u0 OF CSort ⇒c4 | CHead c  ⇒c

                                        eq
                                          C
                                          λe:C.<λ:C.C> CASE e OF CSort ⇒c4 | CHead c  ⇒c (CHead c4 k u2)
                                          λe:C.<λ:C.C> CASE e OF CSort ⇒c4 | CHead c  ⇒c (CHead e1 k0 u0)
                                  end of H4
                                  (h1) 
                                     (H5) 
                                        by (drop_gen_refl . . H3)
                                        we proved eq C (CHead c4 k u2) (CHead e1 k0 u0)
                                        by (f_equal . . . . . previous)
                                        we proved 
                                           eq
                                             K
                                             <λ:C.K> CASE CHead c4 k u2 OF CSort ⇒k | CHead  k1 ⇒k1
                                             <λ:C.K> CASE CHead e1 k0 u0 OF CSort ⇒k | CHead  k1 ⇒k1

                                           eq
                                             K
                                             λe:C.<λ:C.K> CASE e OF CSort ⇒k | CHead  k1 ⇒k1 (CHead c4 k u2)
                                             λe:C.<λ:C.K> CASE e OF CSort ⇒k | CHead  k1 ⇒k1 (CHead e1 k0 u0)
                                     end of H5
                                     (h1) 
                                        (H6) 
                                           by (drop_gen_refl . . H3)
                                           we proved eq C (CHead c4 k u2) (CHead e1 k0 u0)
                                           by (f_equal . . . . . previous)
                                           we proved 
                                              eq
                                                T
                                                <λ:C.T> CASE CHead c4 k u2 OF CSort ⇒u2 | CHead   t⇒t
                                                <λ:C.T> CASE CHead e1 k0 u0 OF CSort ⇒u2 | CHead   t⇒t

                                              eq
                                                T
                                                λe:C.<λ:C.T> CASE e OF CSort ⇒u2 | CHead   t⇒t (CHead c4 k u2)
                                                λe:C.<λ:C.T> CASE e OF CSort ⇒u2 | CHead   t⇒t (CHead e1 k0 u0)
                                        end of H6
                                         suppose H7: eq K k k0
                                         suppose H8: eq C c4 e1
                                           we proceed by induction on H7 to prove ex3_2 C T λe2:C.λu3:T.drop O O (CHead c3 k u1) (CHead e2 k0 u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0
                                              case refl_equal : ⇒
                                                 the thesis becomes ex3_2 C T λe2:C.λu3:T.drop O O (CHead c3 k u1) (CHead e2 k u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0
                                                    consider H6
                                                    we proved 
                                                       eq
                                                         T
                                                         <λ:C.T> CASE CHead c4 k u2 OF CSort ⇒u2 | CHead   t⇒t
                                                         <λ:C.T> CASE CHead e1 k0 u0 OF CSort ⇒u2 | CHead   t⇒t
                                                    that is equivalent to eq T u2 u0
                                                    we proceed by induction on the previous result to prove ex3_2 C T λe2:C.λu3:T.drop O O (CHead c3 k u1) (CHead e2 k u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0
                                                       case refl_equal : ⇒
                                                          the thesis becomes ex3_2 C T λe2:C.λu3:T.drop O O (CHead c3 k u1) (CHead e2 k u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u2
                                                             we proceed by induction on H8 to prove ex3_2 C T λe2:C.λu3:T.drop O O (CHead c3 k u1) (CHead e2 k u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u2
                                                                case refl_equal : ⇒
                                                                   the thesis becomes ex3_2 C T λe2:C.λu3:T.drop O O (CHead c3 k u1) (CHead e2 k u3) λe2:C.λ:T.wcpr0 e2 c4 λ:C.λu3:T.pr0 u3 u2
                                                                      by (drop_refl .)
                                                                      we proved drop O O (CHead c3 k u1) (CHead c3 k u1)
                                                                      by (ex3_2_intro . . . . . . . previous H0 H2)
ex3_2 C T λe2:C.λu3:T.drop O O (CHead c3 k u1) (CHead e2 k u3) λe2:C.λ:T.wcpr0 e2 c4 λ:C.λu3:T.pr0 u3 u2
ex3_2 C T λe2:C.λu3:T.drop O O (CHead c3 k u1) (CHead e2 k u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u2
ex3_2 C T λe2:C.λu3:T.drop O O (CHead c3 k u1) (CHead e2 k u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0
                                           we proved ex3_2 C T λe2:C.λu3:T.drop O O (CHead c3 k u1) (CHead e2 k0 u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0

                                           eq K k k0
                                             →(eq C c4 e1)→(ex3_2 C T λe2:C.λu3:T.drop O O (CHead c3 k u1) (CHead e2 k0 u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0)
                                     end of h1
                                     (h2) 
                                        consider H5
                                        we proved 
                                           eq
                                             K
                                             <λ:C.K> CASE CHead c4 k u2 OF CSort ⇒k | CHead  k1 ⇒k1
                                             <λ:C.K> CASE CHead e1 k0 u0 OF CSort ⇒k | CHead  k1 ⇒k1
eq K k k0
                                     end of h2
                                     by (h1 h2)
(eq C c4 e1)→(ex3_2 C T λe2:C.λu3:T.drop O O (CHead c3 k u1) (CHead e2 k0 u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0)
                                  end of h1
                                  (h2) 
                                     consider H4
                                     we proved 
                                        eq
                                          C
                                          <λ:C.C> CASE CHead c4 k u2 OF CSort ⇒c4 | CHead c  ⇒c
                                          <λ:C.C> CASE CHead e1 k0 u0 OF CSort ⇒c4 | CHead c  ⇒c
eq C c4 e1
                                  end of h2
                                  by (h1 h2)
                                  we proved ex3_2 C T λe2:C.λu3:T.drop O O (CHead c3 k u1) (CHead e2 k0 u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0

                                  ∀e1:C
                                    .∀u0:T
                                      .∀k0:K
                                        .drop O O (CHead c4 k u2) (CHead e1 k0 u0)
                                          →ex3_2 C T λe2:C.λu3:T.drop O O (CHead c3 k u1) (CHead e2 k0 u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0
                         case S ⇒
                            we need to prove 
                            ∀n:nat
                              .∀e1:C
                                  .∀u3:T
                                    .∀k1:K
                                      .drop n O (CHead c4 k u2) (CHead e1 k1 u3)
                                        →ex3_2 C T λe2:C.λu4:T.drop n O (CHead c3 k u1) (CHead e2 k1 u4) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu4:T.pr0 u4 u3
                                →∀e1:C
                                     .∀u3:T
                                       .∀k1:K
                                         .drop (S n) O (CHead c4 k u2) (CHead e1 k1 u3)
                                           →ex3_2 C T λe2:C.λu4:T.drop (S n) O (CHead c3 k u1) (CHead e2 k1 u4) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu4:T.pr0 u4 u3
                               we proceed by induction on k to prove 
                                  ∀n:nat
                                    .∀e1:C
                                        .∀u3:T
                                          .∀k1:K
                                            .drop n O (CHead c4 k u2) (CHead e1 k1 u3)
                                              →ex3_2 C T λe2:C.λu4:T.drop n O (CHead c3 k u1) (CHead e2 k1 u4) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu4:T.pr0 u4 u3
                                      →∀e1:C
                                           .∀u3:T
                                             .∀k1:K
                                               .drop (S n) O (CHead c4 k u2) (CHead e1 k1 u3)
                                                 →ex3_2 C T λe2:C.λu4:T.drop (S n) O (CHead c3 k u1) (CHead e2 k1 u4) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu4:T.pr0 u4 u3
                                  case Bind : b:B ⇒
                                     the thesis becomes 
                                     ∀n:nat
                                       .∀e1:C
                                           .∀u3:T
                                             .∀k0:K
                                               .drop n O (CHead c4 (Bind b) u2) (CHead e1 k0 u3)
                                                 →ex3_2 C T λe2:C.λu4:T.drop n O (CHead c3 (Bind b) u1) (CHead e2 k0 u4) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu4:T.pr0 u4 u3
                                         →∀e1:C
                                              .∀u0:T
                                                .∀k0:K
                                                  .∀H4:drop (S n) O (CHead c4 (Bind b) u2) (CHead e1 k0 u0)
                                                    .ex3_2 C T λe2:C.λu3:T.drop (S n) O (CHead c3 (Bind b) u1) (CHead e2 k0 u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0
                                         assume n: nat
                                         suppose : 
                                            ∀e1:C
                                              .∀u3:T
                                                .∀k0:K
                                                  .drop n O (CHead c4 (Bind b) u2) (CHead e1 k0 u3)
                                                    →ex3_2 C T λe2:C.λu4:T.drop n O (CHead c3 (Bind b) u1) (CHead e2 k0 u4) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu4:T.pr0 u4 u3
                                         assume e1: C
                                         assume u0: T
                                         assume k0: K
                                         suppose H4: drop (S n) O (CHead c4 (Bind b) u2) (CHead e1 k0 u0)
                                           (H5) 
                                              by (drop_gen_drop . . . . . H4)
                                              we proved drop (r (Bind b) n) O c4 (CHead e1 k0 u0)
                                              that is equivalent to drop n O c4 (CHead e1 k0 u0)
                                              by (H1 . . . . previous)
ex3_2 C T λe2:C.λu2:T.drop n O c3 (CHead e2 k0 u2) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu2:T.pr0 u2 u0
                                           end of H5
                                           we proceed by induction on H5 to prove ex3_2 C T λe2:C.λu3:T.drop (S n) O (CHead c3 (Bind b) u1) (CHead e2 k0 u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0
                                              case ex3_2_intro : x0:C x1:T H6:drop n O c3 (CHead x0 k0 x1) H7:wcpr0 x0 e1 H8:pr0 x1 u0 ⇒
                                                 the thesis becomes ex3_2 C T λe2:C.λu3:T.drop (S n) O (CHead c3 (Bind b) u1) (CHead e2 k0 u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0
                                                    consider H6
                                                    we proved drop n O c3 (CHead x0 k0 x1)
                                                    that is equivalent to drop (r (Bind b) n) O c3 (CHead x0 k0 x1)
                                                    by (drop_drop . . . . previous .)
                                                    we proved drop (S n) O (CHead c3 (Bind b) u1) (CHead x0 k0 x1)
                                                    by (ex3_2_intro . . . . . . . previous H7 H8)
ex3_2 C T λe2:C.λu3:T.drop (S n) O (CHead c3 (Bind b) u1) (CHead e2 k0 u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0
                                           we proved ex3_2 C T λe2:C.λu3:T.drop (S n) O (CHead c3 (Bind b) u1) (CHead e2 k0 u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0

                                           ∀n:nat
                                             .∀e1:C
                                                 .∀u3:T
                                                   .∀k0:K
                                                     .drop n O (CHead c4 (Bind b) u2) (CHead e1 k0 u3)
                                                       →ex3_2 C T λe2:C.λu4:T.drop n O (CHead c3 (Bind b) u1) (CHead e2 k0 u4) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu4:T.pr0 u4 u3
                                               →∀e1:C
                                                    .∀u0:T
                                                      .∀k0:K
                                                        .∀H4:drop (S n) O (CHead c4 (Bind b) u2) (CHead e1 k0 u0)
                                                          .ex3_2 C T λe2:C.λu3:T.drop (S n) O (CHead c3 (Bind b) u1) (CHead e2 k0 u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0
                                  case Flat : f:F ⇒
                                     the thesis becomes 
                                     ∀n:nat
                                       .∀e1:C
                                           .∀u3:T
                                             .∀k0:K
                                               .drop n O (CHead c4 (Flat f) u2) (CHead e1 k0 u3)
                                                 →ex3_2 C T λe2:C.λu4:T.drop n O (CHead c3 (Flat f) u1) (CHead e2 k0 u4) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu4:T.pr0 u4 u3
                                         →∀e1:C
                                              .∀u0:T
                                                .∀k0:K
                                                  .∀H4:drop (S n) O (CHead c4 (Flat f) u2) (CHead e1 k0 u0)
                                                    .ex3_2 C T λe2:C.λu3:T.drop (S n) O (CHead c3 (Flat f) u1) (CHead e2 k0 u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0
                                         assume n: nat
                                         suppose : 
                                            ∀e1:C
                                              .∀u3:T
                                                .∀k0:K
                                                  .drop n O (CHead c4 (Flat f) u2) (CHead e1 k0 u3)
                                                    →ex3_2 C T λe2:C.λu4:T.drop n O (CHead c3 (Flat f) u1) (CHead e2 k0 u4) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu4:T.pr0 u4 u3
                                         assume e1: C
                                         assume u0: T
                                         assume k0: K
                                         suppose H4: drop (S n) O (CHead c4 (Flat f) u2) (CHead e1 k0 u0)
                                           (H5) 
                                              by (drop_gen_drop . . . . . H4)
                                              we proved drop (r (Flat f) n) O c4 (CHead e1 k0 u0)
                                              that is equivalent to drop (S n) O c4 (CHead e1 k0 u0)
                                              by (H1 . . . . previous)
ex3_2 C T λe2:C.λu2:T.drop (S n) O c3 (CHead e2 k0 u2) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu2:T.pr0 u2 u0
                                           end of H5
                                           we proceed by induction on H5 to prove ex3_2 C T λe2:C.λu3:T.drop (S n) O (CHead c3 (Flat f) u1) (CHead e2 k0 u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0
                                              case ex3_2_intro : x0:C x1:T H6:drop (S n) O c3 (CHead x0 k0 x1) H7:wcpr0 x0 e1 H8:pr0 x1 u0 ⇒
                                                 the thesis becomes ex3_2 C T λe2:C.λu3:T.drop (S n) O (CHead c3 (Flat f) u1) (CHead e2 k0 u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0
                                                    consider H6
                                                    we proved drop (S n) O c3 (CHead x0 k0 x1)
                                                    that is equivalent to drop (r (Flat f) n) O c3 (CHead x0 k0 x1)
                                                    by (drop_drop . . . . previous .)
                                                    we proved drop (S n) O (CHead c3 (Flat f) u1) (CHead x0 k0 x1)
                                                    by (ex3_2_intro . . . . . . . previous H7 H8)
ex3_2 C T λe2:C.λu3:T.drop (S n) O (CHead c3 (Flat f) u1) (CHead e2 k0 u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0
                                           we proved ex3_2 C T λe2:C.λu3:T.drop (S n) O (CHead c3 (Flat f) u1) (CHead e2 k0 u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0

                                           ∀n:nat
                                             .∀e1:C
                                                 .∀u3:T
                                                   .∀k0:K
                                                     .drop n O (CHead c4 (Flat f) u2) (CHead e1 k0 u3)
                                                       →ex3_2 C T λe2:C.λu4:T.drop n O (CHead c3 (Flat f) u1) (CHead e2 k0 u4) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu4:T.pr0 u4 u3
                                               →∀e1:C
                                                    .∀u0:T
                                                      .∀k0:K
                                                        .∀H4:drop (S n) O (CHead c4 (Flat f) u2) (CHead e1 k0 u0)
                                                          .ex3_2 C T λe2:C.λu3:T.drop (S n) O (CHead c3 (Flat f) u1) (CHead e2 k0 u3) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu3:T.pr0 u3 u0

                                  ∀n:nat
                                    .∀e1:C
                                        .∀u3:T
                                          .∀k1:K
                                            .drop n O (CHead c4 k u2) (CHead e1 k1 u3)
                                              →ex3_2 C T λe2:C.λu4:T.drop n O (CHead c3 k u1) (CHead e2 k1 u4) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu4:T.pr0 u4 u3
                                      →∀e1:C
                                           .∀u3:T
                                             .∀k1:K
                                               .drop (S n) O (CHead c4 k u2) (CHead e1 k1 u3)
                                                 →ex3_2 C T λe2:C.λu4:T.drop (S n) O (CHead c3 k u1) (CHead e2 k1 u4) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu4:T.pr0 u4 u3
                      we proved 
                         ∀e1:C
                           .∀u3:T
                             .∀k0:K
                               .drop h O (CHead c4 k u2) (CHead e1 k0 u3)
                                 →ex3_2 C T λe2:C.λu4:T.drop h O (CHead c3 k u1) (CHead e2 k0 u4) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu4:T.pr0 u4 u3

                      ∀h:nat
                        .∀e1:C
                          .∀u3:T
                            .∀k0:K
                              .drop h O (CHead c4 k u2) (CHead e1 k0 u3)
                                →ex3_2 C T λe2:C.λu4:T.drop h O (CHead c3 k u1) (CHead e2 k0 u4) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu4:T.pr0 u4 u3
          we proved 
             ∀h:nat
               .∀e1:C
                 .∀u1:T
                   .∀k:K
                     .drop h O c1 (CHead e1 k u1)
                       →ex3_2 C T λe2:C.λu2:T.drop h O c2 (CHead e2 k u2) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu2:T.pr0 u2 u1
       we proved 
          ∀c1:C
            .∀c2:C
              .wcpr0 c2 c1
                →∀h:nat
                     .∀e1:C
                       .∀u1:T
                         .∀k:K
                           .drop h O c1 (CHead e1 k u1)
                             →ex3_2 C T λe2:C.λu2:T.drop h O c2 (CHead e2 k u2) λe2:C.λ:T.wcpr0 e2 e1 λ:C.λu2:T.pr0 u2 u1