DEFINITION csubc_drop_conf_rev()
TYPE =
       g:G
         .c2:C
           .e2:C
             .d:nat
               .h:nat
                 .(drop h d c2 e2)e1:C.(csubc g e1 e2)(ex2 C λc1:C.drop h d c1 e1 λc1:C.csubc g c1 c2)
BODY =
        assume gG
        assume c2C
          we proceed by induction on c2 to prove 
             e2:C
               .d:nat
                 .h:nat
                   .(drop h d c2 e2)e1:C.(csubc g e1 e2)(ex2 C λc1:C.drop h d c1 e1 λc1:C.csubc g c1 c2)
             case CSort : n:nat 
                the thesis becomes 
                e2:C
                  .d:nat
                    .h:nat
                      .H:drop h d (CSort n) e2
                        .e1:C.H0:(csubc g e1 e2).(ex2 C λc1:C.drop h d c1 e1 λc1:C.csubc g c1 (CSort n))
                    assume e2C
                    assume dnat
                    assume hnat
                    suppose Hdrop h d (CSort n) e2
                    assume e1C
                    suppose H0csubc g e1 e2
                      by (drop_gen_sort . . . . H)
                      we proved and3 (eq C e2 (CSort n)) (eq nat h O) (eq nat d O)
                      we proceed by induction on the previous result to prove ex2 C λc1:C.drop h d c1 e1 λc1:C.csubc g c1 (CSort n)
                         case and3_intro : H1:eq C e2 (CSort n) H2:eq nat h O H3:eq nat d O 
                            the thesis becomes ex2 C λc1:C.drop h d c1 e1 λc1:C.csubc g c1 (CSort n)
                               (H4
                                  we proceed by induction on H1 to prove csubc g e1 (CSort n)
                                     case refl_equal : 
                                        the thesis becomes the hypothesis H0
csubc g e1 (CSort n)
                               end of H4
                               by (drop_refl .)
                               we proved drop O O e1 e1
                               by (ex_intro2 . . . . previous H4)
                               we proved ex2 C λc1:C.drop O O c1 e1 λc1:C.csubc g c1 (CSort n)
                               by (eq_ind_r . . . previous . H3)
                               we proved ex2 C λc1:C.drop O d c1 e1 λc1:C.csubc g c1 (CSort n)
                               by (eq_ind_r . . . previous . H2)
ex2 C λc1:C.drop h d c1 e1 λc1:C.csubc g c1 (CSort n)
                      we proved ex2 C λc1:C.drop h d c1 e1 λc1:C.csubc g c1 (CSort n)

                      e2:C
                        .d:nat
                          .h:nat
                            .H:drop h d (CSort n) e2
                              .e1:C.H0:(csubc g e1 e2).(ex2 C λc1:C.drop h d c1 e1 λc1:C.csubc g c1 (CSort n))
             case CHead : c:C k:K t:T 
                the thesis becomes 
                e2:C
                  .d:nat
                    .h:nat
                      .drop h d (CHead c k t) e2
                        e1:C.(csubc g e1 e2)(ex2 C λc1:C.drop h d c1 e1 λc1:C.csubc g c1 (CHead c k t))
                (H) by induction hypothesis we know 
                   e2:C
                     .d:nat
                       .h:nat
                         .(drop h d c e2)e1:C.(csubc g e1 e2)(ex2 C λc1:C.drop h d c1 e1 λc1:C.csubc g c1 c)
                    assume e2C
                    assume dnat
                      we proceed by induction on d to prove 
                         h:nat
                           .drop h d (CHead c k t) e2
                             e1:C.(csubc g e1 e2)(ex2 C λc1:C.drop h d c1 e1 λc1:C.csubc g c1 (CHead c k t))
                         case O : 
                            the thesis becomes 
                            h:nat
                              .drop h O (CHead c k t) e2
                                e1:C.(csubc g e1 e2)(ex2 C λc1:C.drop h O c1 e1 λc1:C.csubc g c1 (CHead c k t))
                               assume hnat
                                  we proceed by induction on h to prove 
                                     drop h O (CHead c k t) e2
                                       e1:C.(csubc g e1 e2)(ex2 C λc1:C.drop h O c1 e1 λc1:C.csubc g c1 (CHead c k t))
                                     case O : 
                                        the thesis becomes 
                                        drop O O (CHead c k t) e2
                                          e1:C.(csubc g e1 e2)(ex2 C λc1:C.drop O O c1 e1 λc1:C.csubc g c1 (CHead c k t))
                                            suppose H0drop O O (CHead c k t) e2
                                            assume e1C
                                            suppose H1csubc g e1 e2
                                              (H2
                                                 by (drop_gen_refl . . H0)
                                                 we proved eq C (CHead c k t) e2
                                                 by (eq_ind_r . . . H1 . previous)
csubc g e1 (CHead c k t)
                                              end of H2
                                              by (drop_refl .)
                                              we proved drop O O e1 e1
                                              by (ex_intro2 . . . . previous H2)
                                              we proved ex2 C λc1:C.drop O O c1 e1 λc1:C.csubc g c1 (CHead c k t)

                                              drop O O (CHead c k t) e2
                                                e1:C.(csubc g e1 e2)(ex2 C λc1:C.drop O O c1 e1 λc1:C.csubc g c1 (CHead c k t))
                                     case S : n:nat 
                                        the thesis becomes 
                                        H1:drop (S n) O (CHead c k t) e2
                                          .e1:C.H2:(csubc g e1 e2).(ex2 C λc1:C.drop (S n) O c1 e1 λc1:C.csubc g c1 (CHead c k t))
                                        () by induction hypothesis we know 
                                           drop n O (CHead c k t) e2
                                             e1:C.(csubc g e1 e2)(ex2 C λc1:C.drop n O c1 e1 λc1:C.csubc g c1 (CHead c k t))
                                            suppose H1drop (S n) O (CHead c k t) e2
                                            assume e1C
                                            suppose H2csubc g e1 e2
                                              (H_x
                                                 by (drop_gen_drop . . . . . H1)
                                                 we proved drop (r k n) O c e2
                                                 by (H . . . previous . H2)
ex2 C λc1:C.drop (r k n) O c1 e1 λc1:C.csubc g c1 c
                                              end of H_x
                                              (H3consider H_x
                                              we proceed by induction on H3 to prove ex2 C λc1:C.drop (S n) O c1 e1 λc1:C.csubc g c1 (CHead c k t)
                                                 case ex_intro2 : x:C H4:drop (r k n) O x e1 H5:csubc g x c 
                                                    the thesis becomes ex2 C λc1:C.drop (S n) O c1 e1 λc1:C.csubc g c1 (CHead c k t)
                                                       (h1
                                                          by (drop_drop . . . . H4 .)
drop (S n) O (CHead x k t) e1
                                                       end of h1
                                                       (h2
                                                          by (csubc_head . . . H5 . .)
csubc g (CHead x k t) (CHead c k t)
                                                       end of h2
                                                       by (ex_intro2 . . . . h1 h2)
ex2 C λc1:C.drop (S n) O c1 e1 λc1:C.csubc g c1 (CHead c k t)
                                              we proved ex2 C λc1:C.drop (S n) O c1 e1 λc1:C.csubc g c1 (CHead c k t)

                                              H1:drop (S n) O (CHead c k t) e2
                                                .e1:C.H2:(csubc g e1 e2).(ex2 C λc1:C.drop (S n) O c1 e1 λc1:C.csubc g c1 (CHead c k t))
                                  we proved 
                                     drop h O (CHead c k t) e2
                                       e1:C.(csubc g e1 e2)(ex2 C λc1:C.drop h O c1 e1 λc1:C.csubc g c1 (CHead c k t))

                                  h:nat
                                    .drop h O (CHead c k t) e2
                                      e1:C.(csubc g e1 e2)(ex2 C λc1:C.drop h O c1 e1 λc1:C.csubc g c1 (CHead c k t))
                         case S : n:nat 
                            the thesis becomes 
                            h:nat
                              .H1:drop h (S n) (CHead c k t) e2
                                .e1:C.H2:(csubc g e1 e2).(ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k t))
                            (H0) by induction hypothesis we know 
                               h:nat
                                 .drop h n (CHead c k t) e2
                                   e1:C.(csubc g e1 e2)(ex2 C λc1:C.drop h n c1 e1 λc1:C.csubc g c1 (CHead c k t))
                                assume hnat
                                suppose H1drop h (S n) (CHead c k t) e2
                                assume e1C
                                suppose H2csubc g e1 e2
                                  by (drop_gen_skip_l . . . . . . H1)
                                  we proved 
                                     ex3_2
                                       C
                                       T
                                       λe:C.λv:T.eq C e2 (CHead e k v)
                                       λ:C.λv:T.eq T t (lift h (r k n) v)
                                       λe:C.λ:T.drop h (r k n) c e
                                  we proceed by induction on the previous result to prove ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k t)
                                     case ex3_2_intro : x0:C x1:T H3:eq C e2 (CHead x0 k x1) H4:eq T t (lift h (r k n) x1) H5:drop h (r k n) c x0 
                                        the thesis becomes ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k t)
                                           (H6
                                              we proceed by induction on H3 to prove csubc g e1 (CHead x0 k x1)
                                                 case refl_equal : 
                                                    the thesis becomes the hypothesis H2
csubc g e1 (CHead x0 k x1)
                                           end of H6
                                           (H7
                                              we proceed by induction on H3 to prove 
                                                 h0:nat
                                                   .drop h0 n (CHead c k t) (CHead x0 k x1)
                                                     e3:C
                                                          .csubc g e3 (CHead x0 k x1)
                                                            ex2 C λc1:C.drop h0 n c1 e3 λc1:C.csubc g c1 (CHead c k t)
                                                 case refl_equal : 
                                                    the thesis becomes the hypothesis H0

                                                 h0:nat
                                                   .drop h0 n (CHead c k t) (CHead x0 k x1)
                                                     e3:C
                                                          .csubc g e3 (CHead x0 k x1)
                                                            ex2 C λc1:C.drop h0 n c1 e3 λc1:C.csubc g c1 (CHead c k t)
                                           end of H7
                                           (H8
                                              we proceed by induction on H4 to prove 
                                                 h0:nat
                                                   .drop h0 n (CHead c k (lift h (r k n) x1)) (CHead x0 k x1)
                                                     e3:C
                                                          .csubc g e3 (CHead x0 k x1)
                                                            ex2 C λc1:C.drop h0 n c1 e3 λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                                 case refl_equal : 
                                                    the thesis becomes the hypothesis H7

                                                 h0:nat
                                                   .drop h0 n (CHead c k (lift h (r k n) x1)) (CHead x0 k x1)
                                                     e3:C
                                                          .csubc g e3 (CHead x0 k x1)
                                                            ex2 C λc1:C.drop h0 n c1 e3 λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                           end of H8
                                           (H_x
                                              by (csubc_gen_head_r . . . . . H6)

                                                 or3
                                                   ex2 C λc1:C.eq C e1 (CHead c1 k x1) λc1:C.csubc g c1 x0
                                                   ex5_3
                                                     C
                                                     T
                                                     A
                                                     λ:C.λ:T.λ:A.eq K k (Bind Abbr)
                                                     λc1:C.λv:T.λ:A.eq C e1 (CHead c1 (Bind Abst) v)
                                                     λc1:C.λ:T.λ:A.csubc g c1 x0
                                                     λc1:C.λv:T.λa:A.sc3 g (asucc g a) c1 v
                                                     λ:C.λ:T.λa:A.sc3 g a x0 x1
                                                   ex4_3
                                                     B
                                                     C
                                                     T
                                                     λ:B.λc1:C.λv1:T.eq C e1 (CHead c1 (Bind Void) v1)
                                                     λb:B.λ:C.λ:T.eq K k (Bind b)
                                                     λb:B.λ:C.λ:T.not (eq B b Void)
                                                     λ:B.λc1:C.λ:T.csubc g c1 x0
                                           end of H_x
                                           (H9consider H_x
                                           we proceed by induction on H9 to prove ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                              case or3_intro0 : H10:ex2 C λc1:C.eq C e1 (CHead c1 k x1) λc1:C.csubc g c1 x0 
                                                 the thesis becomes ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                                    we proceed by induction on H10 to prove ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                                       case ex_intro2 : x:C H11:eq C e1 (CHead x k x1) H12:csubc g x x0 
                                                          the thesis becomes ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                                             (H_x0
                                                                by (H . . . H5 . H12)
ex2 C λc1:C.drop h (r k n) c1 x λc1:C.csubc g c1 c
                                                             end of H_x0
                                                             (H13consider H_x0
                                                             we proceed by induction on H13 to prove 
                                                                ex2
                                                                  C
                                                                  λc1:C.drop h (S n) c1 (CHead x k x1)
                                                                  λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                                                case ex_intro2 : x2:C H14:drop h (r k n) x2 x H15:csubc g x2 c 
                                                                   the thesis becomes 
                                                                   ex2
                                                                     C
                                                                     λc1:C.drop h (S n) c1 (CHead x k x1)
                                                                     λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                                                      (h1
                                                                         by (drop_skip . . . . . H14 .)
drop h (S n) (CHead x2 k (lift h (r k n) x1)) (CHead x k x1)
                                                                      end of h1
                                                                      (h2
                                                                         by (csubc_head . . . H15 . .)

                                                                            csubc
                                                                              g
                                                                              CHead x2 k (lift h (r k n) x1)
                                                                              CHead c k (lift h (r k n) x1)
                                                                      end of h2
                                                                      by (ex_intro2 . . . . h1 h2)

                                                                         ex2
                                                                           C
                                                                           λc1:C.drop h (S n) c1 (CHead x k x1)
                                                                           λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                                             we proved 
                                                                ex2
                                                                  C
                                                                  λc1:C.drop h (S n) c1 (CHead x k x1)
                                                                  λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                                             by (eq_ind_r . . . previous . H11)
ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                              case or3_intro1 : H10:ex5_3 C T A λ:C.λ:T.λ:A.eq K k (Bind Abbrλc1:C.λv:T.λ:A.eq C e1 (CHead c1 (Bind Abst) v) λc1:C.λ:T.λ:A.csubc g c1 x0 λc1:C.λv:T.λa:A.sc3 g (asucc g a) c1 v λ:C.λ:T.λa:A.sc3 g a x0 x1 
                                                 the thesis becomes ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                                    we proceed by induction on H10 to prove ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                                       case ex5_3_intro : x2:C x3:T x4:A H11:eq K k (Bind Abbr) H12:eq C e1 (CHead x2 (Bind Abst) x3) H13:csubc g x2 x0 H14:sc3 g (asucc g x4) x2 x3 H15:sc3 g x4 x0 x1 
                                                          the thesis becomes ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                                             (H17
                                                                we proceed by induction on H11 to prove drop h (r (Bind Abbr) n) c x0
                                                                   case refl_equal : 
                                                                      the thesis becomes the hypothesis H5
drop h (r (Bind Abbr) n) c x0
                                                             end of H17
                                                             (H_x0
                                                                by (H . . . H17 . H13)
ex2 C λc1:C.drop h (r (Bind Abbr) n) c1 x2 λc1:C.csubc g c1 c
                                                             end of H_x0
                                                             (H18consider H_x0
                                                             consider H18
                                                             we proved ex2 C λc1:C.drop h (r (Bind Abbr) n) c1 x2 λc1:C.csubc g c1 c
                                                             that is equivalent to ex2 C λc1:C.drop h n c1 x2 λc1:C.csubc g c1 c
                                                             we proceed by induction on the previous result to prove 
                                                                ex2
                                                                  C
                                                                  λc1:C.drop h (S n) c1 (CHead x2 (Bind Abst) x3)
                                                                  λc1:C.csubc g c1 (CHead c (Bind Abbr) (lift h (r (Bind Abbr) n) x1))
                                                                case ex_intro2 : x:C H19:drop h n x x2 H20:csubc g x c 
                                                                   the thesis becomes 
                                                                   ex2
                                                                     C
                                                                     λc1:C.drop h (S n) c1 (CHead x2 (Bind Abst) x3)
                                                                     λc1:C.csubc g c1 (CHead c (Bind Abbr) (lift h (r (Bind Abbr) n) x1))
                                                                      (h1
                                                                         by (drop_skip_bind . . . . H19 . .)

                                                                            drop
                                                                              h
                                                                              S n
                                                                              CHead x (Bind Abst) (lift h n x3)
                                                                              CHead x2 (Bind Abst) x3
                                                                      end of h1
                                                                      (h2
                                                                         (h1
                                                                            by (sc3_lift . . . . H14 . . . H19)
sc3 g (asucc g x4) x (lift h n x3)
                                                                         end of h1
                                                                         (h2
                                                                            by (sc3_lift . . . . H15 . . . H17)
sc3 g x4 c (lift h (r (Bind Abbr) n) x1)
                                                                         end of h2
                                                                         by (csubc_abst . . . H20 . . h1 . h2)

                                                                            csubc
                                                                              g
                                                                              CHead x (Bind Abst) (lift h n x3)
                                                                              CHead c (Bind Abbr) (lift h (r (Bind Abbr) n) x1)
                                                                      end of h2
                                                                      by (ex_intro2 . . . . h1 h2)

                                                                         ex2
                                                                           C
                                                                           λc1:C.drop h (S n) c1 (CHead x2 (Bind Abst) x3)
                                                                           λc1:C.csubc g c1 (CHead c (Bind Abbr) (lift h (r (Bind Abbr) n) x1))
                                                             we proved 
                                                                ex2
                                                                  C
                                                                  λc1:C.drop h (S n) c1 (CHead x2 (Bind Abst) x3)
                                                                  λc1:C.csubc g c1 (CHead c (Bind Abbr) (lift h (r (Bind Abbr) n) x1))
                                                             by (eq_ind_r . . . previous . H11)
                                                             we proved 
                                                                ex2
                                                                  C
                                                                  λc1:C.drop h (S n) c1 (CHead x2 (Bind Abst) x3)
                                                                  λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                                             by (eq_ind_r . . . previous . H12)
ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                              case or3_intro2 : H10:ex4_3 B C T λ:B.λc1:C.λv1:T.eq C e1 (CHead c1 (Bind Void) v1) λb:B.λ:C.λ:T.eq K k (Bind b) λb:B.λ:C.λ:T.not (eq B b Voidλ:B.λc1:C.λ:T.csubc g c1 x0 
                                                 the thesis becomes ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                                    we proceed by induction on H10 to prove ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                                       case ex4_3_intro : x2:B x3:C x4:T H11:eq C e1 (CHead x3 (Bind Void) x4) H12:eq K k (Bind x2) H13:not (eq B x2 Void) H14:csubc g x3 x0 
                                                          the thesis becomes ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                                             (H16
                                                                we proceed by induction on H12 to prove drop h (r (Bind x2) n) c x0
                                                                   case refl_equal : 
                                                                      the thesis becomes the hypothesis H5
drop h (r (Bind x2) n) c x0
                                                             end of H16
                                                             (H_x0
                                                                by (H . . . H16 . H14)
ex2 C λc1:C.drop h (r (Bind x2) n) c1 x3 λc1:C.csubc g c1 c
                                                             end of H_x0
                                                             (H17consider H_x0
                                                             consider H17
                                                             we proved ex2 C λc1:C.drop h (r (Bind x2) n) c1 x3 λc1:C.csubc g c1 c
                                                             that is equivalent to ex2 C λc1:C.drop h n c1 x3 λc1:C.csubc g c1 c
                                                             we proceed by induction on the previous result to prove 
                                                                ex2
                                                                  C
                                                                  λc1:C.drop h (S n) c1 (CHead x3 (Bind Void) x4)
                                                                  λc1:C.csubc g c1 (CHead c (Bind x2) (lift h (r (Bind x2) n) x1))
                                                                case ex_intro2 : x:C H18:drop h n x x3 H19:csubc g x c 
                                                                   the thesis becomes 
                                                                   ex2
                                                                     C
                                                                     λc1:C.drop h (S n) c1 (CHead x3 (Bind Void) x4)
                                                                     λc1:C.csubc g c1 (CHead c (Bind x2) (lift h (r (Bind x2) n) x1))
                                                                      (h1
                                                                         by (drop_skip_bind . . . . H18 . .)

                                                                            drop
                                                                              h
                                                                              S n
                                                                              CHead x (Bind Void) (lift h n x4)
                                                                              CHead x3 (Bind Void) x4
                                                                      end of h1
                                                                      (h2
                                                                         by (csubc_void . . . H19 . H13 . .)

                                                                            csubc
                                                                              g
                                                                              CHead x (Bind Void) (lift h n x4)
                                                                              CHead c (Bind x2) (lift h (r (Bind x2) n) x1)
                                                                      end of h2
                                                                      by (ex_intro2 . . . . h1 h2)

                                                                         ex2
                                                                           C
                                                                           λc1:C.drop h (S n) c1 (CHead x3 (Bind Void) x4)
                                                                           λc1:C.csubc g c1 (CHead c (Bind x2) (lift h (r (Bind x2) n) x1))
                                                             we proved 
                                                                ex2
                                                                  C
                                                                  λc1:C.drop h (S n) c1 (CHead x3 (Bind Void) x4)
                                                                  λc1:C.csubc g c1 (CHead c (Bind x2) (lift h (r (Bind x2) n) x1))
                                                             by (eq_ind_r . . . previous . H12)
                                                             we proved 
                                                                ex2
                                                                  C
                                                                  λc1:C.drop h (S n) c1 (CHead x3 (Bind Void) x4)
                                                                  λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                                             by (eq_ind_r . . . previous . H11)
ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                           we proved ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k (lift h (r k n) x1))
                                           by (eq_ind_r . . . previous . H4)
ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k t)
                                  we proved ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k t)

                                  h:nat
                                    .H1:drop h (S n) (CHead c k t) e2
                                      .e1:C.H2:(csubc g e1 e2).(ex2 C λc1:C.drop h (S n) c1 e1 λc1:C.csubc g c1 (CHead c k t))
                      we proved 
                         h:nat
                           .drop h d (CHead c k t) e2
                             e1:C.(csubc g e1 e2)(ex2 C λc1:C.drop h d c1 e1 λc1:C.csubc g c1 (CHead c k t))

                      e2:C
                        .d:nat
                          .h:nat
                            .drop h d (CHead c k t) e2
                              e1:C.(csubc g e1 e2)(ex2 C λc1:C.drop h d c1 e1 λc1:C.csubc g c1 (CHead c k t))
          we proved 
             e2:C
               .d:nat
                 .h:nat
                   .(drop h d c2 e2)e1:C.(csubc g e1 e2)(ex2 C λc1:C.drop h d c1 e1 λc1:C.csubc g c1 c2)
       we proved 
          g:G
            .c2:C
              .e2:C
                .d:nat
                  .h:nat
                    .(drop h d c2 e2)e1:C.(csubc g e1 e2)(ex2 C λc1:C.drop h d c1 e1 λc1:C.csubc g c1 c2)