DEFINITION ty3_arity()
TYPE =
       g:G.c:C.t1:T.t2:T.(ty3 g c t1 t2)(ex2 A λa1:A.arity g c t1 a1 λa1:A.arity g c t2 (asucc g a1))
BODY =
        assume gG
        assume cC
        assume t1T
        assume t2T
        suppose Hty3 g c t1 t2
          we proceed by induction on H to prove ex2 A λa1:A.arity g c t1 a1 λa1:A.arity g c t2 (asucc g a1)
             case ty3_conv : c0:C t3:T t:T :ty3 g c0 t3 t u:T t4:T :ty3 g c0 u t4 H4:pc3 c0 t4 t3 
                the thesis becomes ex2 A λa1:A.arity g c0 u a1 λa1:A.arity g c0 t3 (asucc g a1)
                (H1) by induction hypothesis we know ex2 A λa1:A.arity g c0 t3 a1 λa1:A.arity g c0 t (asucc g a1)
                (H3) by induction hypothesis we know ex2 A λa1:A.arity g c0 u a1 λa1:A.arity g c0 t4 (asucc g a1)
                   (H5consider H1
                   we proceed by induction on H5 to prove ex2 A λa1:A.arity g c0 u a1 λa1:A.arity g c0 t3 (asucc g a1)
                      case ex_intro2 : x:A H6:arity g c0 t3 x :arity g c0 t (asucc g x) 
                         the thesis becomes ex2 A λa1:A.arity g c0 u a1 λa1:A.arity g c0 t3 (asucc g a1)
                            (H8consider H3
                            we proceed by induction on H8 to prove ex2 A λa1:A.arity g c0 u a1 λa1:A.arity g c0 t3 (asucc g a1)
                               case ex_intro2 : x0:A H9:arity g c0 u x0 H10:arity g c0 t4 (asucc g x0) 
                                  the thesis becomes ex2 A λa1:A.arity g c0 u a1 λa1:A.arity g c0 t3 (asucc g a1)
                                     (H11consider H4
                                     consider H11
                                     we proved pc3 c0 t4 t3
                                     that is equivalent to ex2 T λt0:T.pr3 c0 t4 t0 λt0:T.pr3 c0 t3 t0
                                     we proceed by induction on the previous result to prove ex2 A λa1:A.arity g c0 u a1 λa1:A.arity g c0 t3 (asucc g a1)
                                        case ex_intro2 : x1:T H12:pr3 c0 t4 x1 H13:pr3 c0 t3 x1 
                                           the thesis becomes ex2 A λa1:A.arity g c0 u a1 λa1:A.arity g c0 t3 (asucc g a1)
                                              (h1
                                                 by (arity_sred_pr3 . . . H12 . . H10)
arity g c0 x1 (asucc g x0)
                                              end of h1
                                              (h2
                                                 by (arity_sred_pr3 . . . H13 . . H6)
arity g c0 x1 x
                                              end of h2
                                              by (arity_mono . . . . h1 . h2)
                                              we proved leq g (asucc g x0) x
                                              by (leq_sym . . . previous)
                                              we proved leq g x (asucc g x0)
                                              by (arity_repl . . . . H6 . previous)
                                              we proved arity g c0 t3 (asucc g x0)
                                              by (ex_intro2 . . . . H9 previous)
ex2 A λa1:A.arity g c0 u a1 λa1:A.arity g c0 t3 (asucc g a1)
ex2 A λa1:A.arity g c0 u a1 λa1:A.arity g c0 t3 (asucc g a1)
ex2 A λa1:A.arity g c0 u a1 λa1:A.arity g c0 t3 (asucc g a1)
ex2 A λa1:A.arity g c0 u a1 λa1:A.arity g c0 t3 (asucc g a1)
             case ty3_sort : c0:C m:nat 
                the thesis becomes 
                ex2
                  A
                  λa1:A.arity g c0 (TSort m) a1
                  λa1:A.arity g c0 (TSort (next g m)) (asucc g a1)
                   (h1
                      by (arity_sort . . .)
arity g c0 (TSort m) (ASort O m)
                   end of h1
                   (h2
                      by (arity_sort . . .)
                      we proved arity g c0 (TSort (next g m)) (ASort O (next g m))
arity g c0 (TSort (next g m)) (asucc g (ASort O m))
                   end of h2
                   by (ex_intro2 . . . . h1 h2)

                      ex2
                        A
                        λa1:A.arity g c0 (TSort m) a1
                        λa1:A.arity g c0 (TSort (next g m)) (asucc g a1)
             case ty3_abbr : n:nat c0:C d:C u:T H0:getl n c0 (CHead d (Bind Abbr) u) t:T :ty3 g d u t 
                the thesis becomes 
                ex2
                  A
                  λa1:A.arity g c0 (TLRef n) a1
                  λa1:A.arity g c0 (lift (S n) O t) (asucc g a1)
                (H2) by induction hypothesis we know ex2 A λa1:A.arity g d u a1 λa1:A.arity g d t (asucc g a1)
                   (H3consider H2
                   we proceed by induction on H3 to prove 
                      ex2
                        A
                        λa1:A.arity g c0 (TLRef n) a1
                        λa1:A.arity g c0 (lift (S n) O t) (asucc g a1)
                      case ex_intro2 : x:A H4:arity g d u x H5:arity g d t (asucc g x) 
                         the thesis becomes 
                         ex2
                           A
                           λa1:A.arity g c0 (TLRef n) a1
                           λa1:A.arity g c0 (lift (S n) O t) (asucc g a1)
                            (h1
                               by (arity_abbr . . . . . H0 . H4)
arity g c0 (TLRef n) x
                            end of h1
                            (h2
                               by (getl_drop . . . . . H0)
                               we proved drop (S n) O c0 d
                               by (arity_lift . . . . H5 . . . previous)
arity g c0 (lift (S n) O t) (asucc g x)
                            end of h2
                            by (ex_intro2 . . . . h1 h2)

                               ex2
                                 A
                                 λa1:A.arity g c0 (TLRef n) a1
                                 λa1:A.arity g c0 (lift (S n) O t) (asucc g a1)

                      ex2
                        A
                        λa1:A.arity g c0 (TLRef n) a1
                        λa1:A.arity g c0 (lift (S n) O t) (asucc g a1)
             case ty3_abst : n:nat c0:C d:C u:T H0:getl n c0 (CHead d (Bind Abst) u) t:T :ty3 g d u t 
                the thesis becomes 
                ex2
                  A
                  λa1:A.arity g c0 (TLRef n) a1
                  λa1:A.arity g c0 (lift (S n) O u) (asucc g a1)
                (H2) by induction hypothesis we know ex2 A λa1:A.arity g d u a1 λa1:A.arity g d t (asucc g a1)
                   (H3consider H2
                   we proceed by induction on H3 to prove 
                      ex2
                        A
                        λa1:A.arity g c0 (TLRef n) a1
                        λa1:A.arity g c0 (lift (S n) O u) (asucc g a1)
                      case ex_intro2 : x:A H4:arity g d u x :arity g d t (asucc g x) 
                         the thesis becomes 
                         ex2
                           A
                           λa1:A.arity g c0 (TLRef n) a1
                           λa1:A.arity g c0 (lift (S n) O u) (asucc g a1)
                            (H_x
                               by (leq_asucc . .)
ex A λa0:A.leq g x (asucc g a0)
                            end of H_x
                            (H6consider H_x
                            we proceed by induction on H6 to prove 
                               ex2
                                 A
                                 λa1:A.arity g c0 (TLRef n) a1
                                 λa1:A.arity g c0 (lift (S n) O u) (asucc g a1)
                               case ex_intro : x0:A H7:leq g x (asucc g x0) 
                                  the thesis becomes 
                                  ex2
                                    A
                                    λa1:A.arity g c0 (TLRef n) a1
                                    λa1:A.arity g c0 (lift (S n) O u) (asucc g a1)
                                     (h1
                                        by (arity_repl . . . . H4 . H7)
                                        we proved arity g d u (asucc g x0)
                                        by (arity_abst . . . . . H0 . previous)
arity g c0 (TLRef n) x0
                                     end of h1
                                     (h2
                                        by (getl_drop . . . . . H0)
                                        we proved drop (S n) O c0 d
                                        by (arity_lift . . . . H4 . . . previous)
                                        we proved arity g c0 (lift (S n) O u) x
                                        by (arity_repl . . . . previous . H7)
arity g c0 (lift (S n) O u) (asucc g x0)
                                     end of h2
                                     by (ex_intro2 . . . . h1 h2)

                                        ex2
                                          A
                                          λa1:A.arity g c0 (TLRef n) a1
                                          λa1:A.arity g c0 (lift (S n) O u) (asucc g a1)

                               ex2
                                 A
                                 λa1:A.arity g c0 (TLRef n) a1
                                 λa1:A.arity g c0 (lift (S n) O u) (asucc g a1)

                      ex2
                        A
                        λa1:A.arity g c0 (TLRef n) a1
                        λa1:A.arity g c0 (lift (S n) O u) (asucc g a1)
             case ty3_bind : c0:C u:T t:T :ty3 g c0 u t b:B t3:T t4:T :ty3 g (CHead c0 (Bind b) u) t3 t4 
                the thesis becomes 
                ex2
                  A
                  λa1:A.arity g c0 (THead (Bind b) u t3) a1
                  λa1:A.arity g c0 (THead (Bind b) u t4) (asucc g a1)
                (H1) by induction hypothesis we know ex2 A λa1:A.arity g c0 u a1 λa1:A.arity g c0 t (asucc g a1)
                (H3) by induction hypothesis we know 
                   ex2
                     A
                     λa1:A.arity g (CHead c0 (Bind b) u) t3 a1
                     λa1:A.arity g (CHead c0 (Bind b) u) t4 (asucc g a1)
                   (H4consider H1
                   we proceed by induction on H4 to prove 
                      ex2
                        A
                        λa1:A.arity g c0 (THead (Bind b) u t3) a1
                        λa1:A.arity g c0 (THead (Bind b) u t4) (asucc g a1)
                      case ex_intro2 : x:A H5:arity g c0 u x :arity g c0 t (asucc g x) 
                         the thesis becomes 
                         ex2
                           A
                           λa1:A.arity g c0 (THead (Bind b) u t3) a1
                           λa1:A.arity g c0 (THead (Bind b) u t4) (asucc g a1)
                            (H7consider H3
                            we proceed by induction on H7 to prove 
                               ex2
                                 A
                                 λa1:A.arity g c0 (THead (Bind b) u t3) a1
                                 λa1:A.arity g c0 (THead (Bind b) u t4) (asucc g a1)
                               case ex_intro2 : x0:A H8:arity g (CHead c0 (Bind b) u) t3 x0 H9:arity g (CHead c0 (Bind b) u) t4 (asucc g x0) 
                                  the thesis becomes 
                                  ex2
                                    A
                                    λa1:A.arity g c0 (THead (Bind b) u t3) a1
                                    λa1:A.arity g c0 (THead (Bind b) u t4) (asucc g a1)
                                     (H_x
                                        by (leq_asucc . .)
ex A λa0:A.leq g x (asucc g a0)
                                     end of H_x
                                     (H10consider H_x
                                     we proceed by induction on H10 to prove 
                                        ex2
                                          A
                                          λa1:A.arity g c0 (THead (Bind b) u t3) a1
                                          λa1:A.arity g c0 (THead (Bind b) u t4) (asucc g a1)
                                        case ex_intro : x1:A H11:leq g x (asucc g x1) 
                                           the thesis becomes 
                                           ex2
                                             A
                                             λa1:A.arity g c0 (THead (Bind b) u t3) a1
                                             λa1:A.arity g c0 (THead (Bind b) u t4) (asucc g a1)
                                               suppose H12arity g (CHead c0 (Bind Abbr) u) t3 x0
                                               suppose H13arity g (CHead c0 (Bind Abbr) u) t4 (asucc g x0)
                                                 (h1
                                                    by (arity_bind . . not_abbr_abst . . . H5 . . H12)
arity g c0 (THead (Bind Abbr) u t3) x0
                                                 end of h1
                                                 (h2
                                                    by (arity_bind . . not_abbr_abst . . . H5 . . H13)
arity g c0 (THead (Bind Abbr) u t4) (asucc g x0)
                                                 end of h2
                                                 by (ex_intro2 . . . . h1 h2)
                                                 we proved 
                                                    ex2
                                                      A
                                                      λa1:A.arity g c0 (THead (Bind Abbr) u t3) a1
                                                      λa1:A.arity g c0 (THead (Bind Abbr) u t4) (asucc g a1)

                                                 arity g (CHead c0 (Bind Abbr) u) t3 x0
                                                   (arity g (CHead c0 (Bind Abbr) u) t4 (asucc g x0)
                                                        (ex2
                                                             A
                                                             λa1:A.arity g c0 (THead (Bind Abbr) u t3) a1
                                                             λa1:A.arity g c0 (THead (Bind Abbr) u t4) (asucc g a1)))
                                               suppose H12arity g (CHead c0 (Bind Abst) u) t3 x0
                                               suppose H13arity g (CHead c0 (Bind Abst) u) t4 (asucc g x0)
                                                 (h1
                                                    by (arity_repl . . . . H5 . H11)
                                                    we proved arity g c0 u (asucc g x1)
                                                    by (arity_head . . . . previous . . H12)
arity g c0 (THead (Bind Abst) u t3) (AHead x1 x0)
                                                 end of h1
                                                 (h2
                                                    (h1
                                                       by (arity_repl . . . . H5 . H11)
                                                       we proved arity g c0 u (asucc g x1)
                                                       by (arity_head . . . . previous . . H13)
arity g c0 (THead (Bind Abst) u t4) (AHead x1 (asucc g x0))
                                                    end of h1
                                                    (h2
                                                       by (leq_refl . .)
                                                       we proved leq g (asucc g (AHead x1 x0)) (asucc g (AHead x1 x0))
leq g (AHead x1 (asucc g x0)) (asucc g (AHead x1 x0))
                                                    end of h2
                                                    by (arity_repl . . . . h1 . h2)
arity g c0 (THead (Bind Abst) u t4) (asucc g (AHead x1 x0))
                                                 end of h2
                                                 by (ex_intro2 . . . . h1 h2)
                                                 we proved 
                                                    ex2
                                                      A
                                                      λa1:A.arity g c0 (THead (Bind Abst) u t3) a1
                                                      λa1:A.arity g c0 (THead (Bind Abst) u t4) (asucc g a1)

                                                 arity g (CHead c0 (Bind Abst) u) t3 x0
                                                   (arity g (CHead c0 (Bind Abst) u) t4 (asucc g x0)
                                                        (ex2
                                                             A
                                                             λa1:A.arity g c0 (THead (Bind Abst) u t3) a1
                                                             λa1:A.arity g c0 (THead (Bind Abst) u t4) (asucc g a1)))
                                               suppose H12arity g (CHead c0 (Bind Void) u) t3 x0
                                               suppose H13arity g (CHead c0 (Bind Void) u) t4 (asucc g x0)
                                                 (h1
                                                    by (sym_not_eq . . . not_abst_void)
                                                    we proved not (eq B Void Abst)
                                                    by (arity_bind . . previous . . . H5 . . H12)
arity g c0 (THead (Bind Void) u t3) x0
                                                 end of h1
                                                 (h2
                                                    by (sym_not_eq . . . not_abst_void)
                                                    we proved not (eq B Void Abst)
                                                    by (arity_bind . . previous . . . H5 . . H13)
arity g c0 (THead (Bind Void) u t4) (asucc g x0)
                                                 end of h2
                                                 by (ex_intro2 . . . . h1 h2)
                                                 we proved 
                                                    ex2
                                                      A
                                                      λa1:A.arity g c0 (THead (Bind Void) u t3) a1
                                                      λa1:A.arity g c0 (THead (Bind Void) u t4) (asucc g a1)

                                                 arity g (CHead c0 (Bind Void) u) t3 x0
                                                   (arity g (CHead c0 (Bind Void) u) t4 (asucc g x0)
                                                        (ex2
                                                             A
                                                             λa1:A.arity g c0 (THead (Bind Void) u t3) a1
                                                             λa1:A.arity g c0 (THead (Bind Void) u t4) (asucc g a1)))
                                              by (previous . H8 H9)

                                                 ex2
                                                   A
                                                   λa1:A.arity g c0 (THead (Bind b) u t3) a1
                                                   λa1:A.arity g c0 (THead (Bind b) u t4) (asucc g a1)

                                        ex2
                                          A
                                          λa1:A.arity g c0 (THead (Bind b) u t3) a1
                                          λa1:A.arity g c0 (THead (Bind b) u t4) (asucc g a1)

                               ex2
                                 A
                                 λa1:A.arity g c0 (THead (Bind b) u t3) a1
                                 λa1:A.arity g c0 (THead (Bind b) u t4) (asucc g a1)

                      ex2
                        A
                        λa1:A.arity g c0 (THead (Bind b) u t3) a1
                        λa1:A.arity g c0 (THead (Bind b) u t4) (asucc g a1)
             case ty3_appl : c0:C w:T u:T :ty3 g c0 w u v:T t:T :ty3 g c0 v (THead (Bind Abst) u t) 
                the thesis becomes 
                ex2
                  A
                  λa1:A.arity g c0 (THead (Flat Appl) w v) a1
                  λa1:A
                    .arity
                      g
                      c0
                      THead (Flat Appl) w (THead (Bind Abst) u t)
                      asucc g a1
                (H1) by induction hypothesis we know ex2 A λa1:A.arity g c0 w a1 λa1:A.arity g c0 u (asucc g a1)
                (H3) by induction hypothesis we know 
                   ex2 A λa1:A.arity g c0 v a1 λa1:A.arity g c0 (THead (Bind Abst) u t) (asucc g a1)
                   (H4consider H1
                   we proceed by induction on H4 to prove 
                      ex2
                        A
                        λa1:A.arity g c0 (THead (Flat Appl) w v) a1
                        λa1:A
                          .arity
                            g
                            c0
                            THead (Flat Appl) w (THead (Bind Abst) u t)
                            asucc g a1
                      case ex_intro2 : x:A H5:arity g c0 w x H6:arity g c0 u (asucc g x) 
                         the thesis becomes 
                         ex2
                           A
                           λa1:A.arity g c0 (THead (Flat Appl) w v) a1
                           λa1:A
                             .arity
                               g
                               c0
                               THead (Flat Appl) w (THead (Bind Abst) u t)
                               asucc g a1
                            (H7consider H3
                            we proceed by induction on H7 to prove 
                               ex2
                                 A
                                 λa1:A.arity g c0 (THead (Flat Appl) w v) a1
                                 λa1:A
                                   .arity
                                     g
                                     c0
                                     THead (Flat Appl) w (THead (Bind Abst) u t)
                                     asucc g a1
                               case ex_intro2 : x0:A H8:arity g c0 v x0 H9:arity g c0 (THead (Bind Abst) u t) (asucc g x0) 
                                  the thesis becomes 
                                  ex2
                                    A
                                    λa1:A.arity g c0 (THead (Flat Appl) w v) a1
                                    λa1:A
                                      .arity
                                        g
                                        c0
                                        THead (Flat Appl) w (THead (Bind Abst) u t)
                                        asucc g a1
                                     (H10
                                        by (arity_gen_abst . . . . . H9)

                                           ex3_2
                                             A
                                             A
                                             λa1:A.λa2:A.eq A (asucc g x0) (AHead a1 a2)
                                             λa1:A.λ:A.arity g c0 u (asucc g a1)
                                             λ:A.λa2:A.arity g (CHead c0 (Bind Abst) u) t a2
                                     end of H10
                                     we proceed by induction on H10 to prove 
                                        ex2
                                          A
                                          λa1:A.arity g c0 (THead (Flat Appl) w v) a1
                                          λa1:A
                                            .arity
                                              g
                                              c0
                                              THead (Flat Appl) w (THead (Bind Abst) u t)
                                              asucc g a1
                                        case ex3_2_intro : x1:A x2:A H11:eq A (asucc g x0) (AHead x1 x2) H12:arity g c0 u (asucc g x1) H13:arity g (CHead c0 (Bind Abst) u) t x2 
                                           the thesis becomes 
                                           ex2
                                             A
                                             λa1:A.arity g c0 (THead (Flat Appl) w v) a1
                                             λa1:A
                                               .arity
                                                 g
                                                 c0
                                                 THead (Flat Appl) w (THead (Bind Abst) u t)
                                                 asucc g a1
                                              (H14
                                                 by (sym_eq . . . H11)
eq A (AHead x1 x2) (asucc g x0)
                                              end of H14
                                              (H15
                                                 by (asucc_gen_head . . . . H14)
ex2 A λa0:A.eq A x0 (AHead x1 a0) λa0:A.eq A x2 (asucc g a0)
                                              end of H15
                                              we proceed by induction on H15 to prove 
                                                 ex2
                                                   A
                                                   λa1:A.arity g c0 (THead (Flat Appl) w v) a1
                                                   λa1:A
                                                     .arity
                                                       g
                                                       c0
                                                       THead (Flat Appl) w (THead (Bind Abst) u t)
                                                       asucc g a1
                                                 case ex_intro2 : x3:A H16:eq A x0 (AHead x1 x3) H17:eq A x2 (asucc g x3) 
                                                    the thesis becomes 
                                                    ex2
                                                      A
                                                      λa1:A.arity g c0 (THead (Flat Appl) w v) a1
                                                      λa1:A
                                                        .arity
                                                          g
                                                          c0
                                                          THead (Flat Appl) w (THead (Bind Abst) u t)
                                                          asucc g a1
                                                       (H18
                                                          we proceed by induction on H17 to prove arity g (CHead c0 (Bind Abst) u) t (asucc g x3)
                                                             case refl_equal : 
                                                                the thesis becomes the hypothesis H13
arity g (CHead c0 (Bind Abst) u) t (asucc g x3)
                                                       end of H18
                                                       (H19
                                                          we proceed by induction on H16 to prove arity g c0 v (AHead x1 x3)
                                                             case refl_equal : 
                                                                the thesis becomes the hypothesis H8
arity g c0 v (AHead x1 x3)
                                                       end of H19
                                                       (h1
                                                          by (arity_mono . . . . H12 . H6)
                                                          we proved leq g (asucc g x1) (asucc g x)
                                                          by (asucc_inj . . . previous)
                                                          we proved leq g x1 x
                                                          by (leq_sym . . . previous)
                                                          we proved leq g x x1
                                                          by (arity_repl . . . . H5 . previous)
                                                          we proved arity g c0 w x1
                                                          by (arity_appl . . . . previous . . H19)
arity g c0 (THead (Flat Appl) w v) x3
                                                       end of h1
                                                       (h2
                                                          by (arity_head . . . . H6 . . H18)
                                                          we proved arity g c0 (THead (Bind Abst) u t) (AHead x (asucc g x3))
                                                          by (arity_appl . . . . H5 . . previous)

                                                             arity
                                                               g
                                                               c0
                                                               THead (Flat Appl) w (THead (Bind Abst) u t)
                                                               asucc g x3
                                                       end of h2
                                                       by (ex_intro2 . . . . h1 h2)

                                                          ex2
                                                            A
                                                            λa1:A.arity g c0 (THead (Flat Appl) w v) a1
                                                            λa1:A
                                                              .arity
                                                                g
                                                                c0
                                                                THead (Flat Appl) w (THead (Bind Abst) u t)
                                                                asucc g a1

                                                 ex2
                                                   A
                                                   λa1:A.arity g c0 (THead (Flat Appl) w v) a1
                                                   λa1:A
                                                     .arity
                                                       g
                                                       c0
                                                       THead (Flat Appl) w (THead (Bind Abst) u t)
                                                       asucc g a1

                                        ex2
                                          A
                                          λa1:A.arity g c0 (THead (Flat Appl) w v) a1
                                          λa1:A
                                            .arity
                                              g
                                              c0
                                              THead (Flat Appl) w (THead (Bind Abst) u t)
                                              asucc g a1

                               ex2
                                 A
                                 λa1:A.arity g c0 (THead (Flat Appl) w v) a1
                                 λa1:A
                                   .arity
                                     g
                                     c0
                                     THead (Flat Appl) w (THead (Bind Abst) u t)
                                     asucc g a1

                      ex2
                        A
                        λa1:A.arity g c0 (THead (Flat Appl) w v) a1
                        λa1:A
                          .arity
                            g
                            c0
                            THead (Flat Appl) w (THead (Bind Abst) u t)
                            asucc g a1
             case ty3_cast : c0:C t3:T t4:T :ty3 g c0 t3 t4 t0:T :ty3 g c0 t4 t0 
                the thesis becomes 
                ex2
                  A
                  λa1:A.arity g c0 (THead (Flat Cast) t4 t3) a1
                  λa1:A.arity g c0 (THead (Flat Cast) t0 t4) (asucc g a1)
                (H1) by induction hypothesis we know ex2 A λa1:A.arity g c0 t3 a1 λa1:A.arity g c0 t4 (asucc g a1)
                (H3) by induction hypothesis we know ex2 A λa1:A.arity g c0 t4 a1 λa1:A.arity g c0 t0 (asucc g a1)
                   (H4consider H1
                   we proceed by induction on H4 to prove 
                      ex2
                        A
                        λa1:A.arity g c0 (THead (Flat Cast) t4 t3) a1
                        λa1:A.arity g c0 (THead (Flat Cast) t0 t4) (asucc g a1)
                      case ex_intro2 : x:A H5:arity g c0 t3 x H6:arity g c0 t4 (asucc g x) 
                         the thesis becomes 
                         ex2
                           A
                           λa1:A.arity g c0 (THead (Flat Cast) t4 t3) a1
                           λa1:A.arity g c0 (THead (Flat Cast) t0 t4) (asucc g a1)
                            (H7consider H3
                            we proceed by induction on H7 to prove 
                               ex2
                                 A
                                 λa1:A.arity g c0 (THead (Flat Cast) t4 t3) a1
                                 λa1:A.arity g c0 (THead (Flat Cast) t0 t4) (asucc g a1)
                               case ex_intro2 : x0:A H8:arity g c0 t4 x0 H9:arity g c0 t0 (asucc g x0) 
                                  the thesis becomes 
                                  ex2
                                    A
                                    λa1:A.arity g c0 (THead (Flat Cast) t4 t3) a1
                                    λa1:A.arity g c0 (THead (Flat Cast) t0 t4) (asucc g a1)
                                     (h1
                                        by (arity_cast . . . . H6 . H5)
arity g c0 (THead (Flat Cast) t4 t3) x
                                     end of h1
                                     (h2
                                        by (arity_mono . . . . H8 . H6)
                                        we proved leq g x0 (asucc g x)
                                        by (asucc_repl . . . previous)
                                        we proved leq g (asucc g x0) (asucc g (asucc g x))
                                        by (arity_repl . . . . H9 . previous)
                                        we proved arity g c0 t0 (asucc g (asucc g x))
                                        by (arity_cast . . . . previous . H6)
arity g c0 (THead (Flat Cast) t0 t4) (asucc g x)
                                     end of h2
                                     by (ex_intro2 . . . . h1 h2)

                                        ex2
                                          A
                                          λa1:A.arity g c0 (THead (Flat Cast) t4 t3) a1
                                          λa1:A.arity g c0 (THead (Flat Cast) t0 t4) (asucc g a1)

                               ex2
                                 A
                                 λa1:A.arity g c0 (THead (Flat Cast) t4 t3) a1
                                 λa1:A.arity g c0 (THead (Flat Cast) t0 t4) (asucc g a1)

                      ex2
                        A
                        λa1:A.arity g c0 (THead (Flat Cast) t4 t3) a1
                        λa1:A.arity g c0 (THead (Flat Cast) t0 t4) (asucc g a1)
          we proved ex2 A λa1:A.arity g c t1 a1 λa1:A.arity g c t2 (asucc g a1)
       we proved g:G.c:C.t1:T.t2:T.(ty3 g c t1 t2)(ex2 A λa1:A.arity g c t1 a1 λa1:A.arity g c t2 (asucc g a1))