DEFINITION pc3_pr2_fsubst0_back()
TYPE =
       c1:C
         .t:T
           .t1:T
             .pr2 c1 t t1
               i:nat
                    .u:T.c2:C.t2:T.(fsubst0 i u c1 t1 c2 t2)e:C.(getl i c1 (CHead e (Bind Abbr) u))(pc3 c2 t t2)
BODY =
        assume c1C
        assume tT
        assume t1T
        suppose Hpr2 c1 t t1
          we proceed by induction on H to prove 
             i:nat
               .u:T.c2:C.t3:T.(fsubst0 i u c1 t1 c2 t3)e:C.(getl i c1 (CHead e (Bind Abbr) u))(pc3 c2 t t3)
             case pr2_free : c:C t2:T t3:T H0:pr0 t2 t3 
                the thesis becomes i:nat.u:T.c2:C.t0:T.H1:(fsubst0 i u c t3 c2 t0).e:C.(getl i c (CHead e (Bind Abbr) u))(pc3 c2 t2 t0)
                    assume inat
                    assume uT
                    assume c2C
                    assume t0T
                    suppose H1fsubst0 i u c t3 c2 t0
                      we proceed by induction on H1 to prove e:C.(getl i c (CHead e (Bind Abbr) u))(pc3 c2 t2 t0)
                         case fsubst0_snd : t4:T H2:subst0 i u t3 t4 
                            the thesis becomes e:C.H3:(getl i c (CHead e (Bind Abbr) u)).(pc3 c t2 t4)
                                assume eC
                                suppose H3getl i c (CHead e (Bind Abbr) u)
                                  (h1
                                     by (pr2_free . . . H0)
pr2 c t2 t3
                                  end of h1
                                  (h2
                                     by (pr0_refl .)
                                     we proved pr0 t3 t3
                                     by (pr2_delta . . . . H3 . . previous . H2)
                                     we proved pr2 c t3 t4
                                     by (pc3_pr2_r . . . previous)
pc3 c t3 t4
                                  end of h2
                                  by (pc3_pr2_u . . . h1 . h2)
                                  we proved pc3 c t2 t4
e:C.H3:(getl i c (CHead e (Bind Abbr) u)).(pc3 c t2 t4)
                         case fsubst0_fst : c0:C :csubst0 i u c c0 
                            the thesis becomes e:C.(getl i c (CHead e (Bind Abbr) u))(pc3 c0 t2 t3)
                                assume eC
                                suppose getl i c (CHead e (Bind Abbr) u)
                                  by (pr2_free . . . H0)
                                  we proved pr2 c0 t2 t3
                                  by (pc3_pr2_r . . . previous)
                                  we proved pc3 c0 t2 t3
e:C.(getl i c (CHead e (Bind Abbr) u))(pc3 c0 t2 t3)
                         case fsubst0_both : t4:T H2:subst0 i u t3 t4 c0:C H3:csubst0 i u c c0 
                            the thesis becomes e:C.H4:(getl i c (CHead e (Bind Abbr) u)).(pc3 c0 t2 t4)
                                assume eC
                                suppose H4getl i c (CHead e (Bind Abbr) u)
                                  (h1by (pr2_free . . . H0) we proved pr2 c0 t2 t3
                                  (h2
                                     (h1
                                        by (le_n .)
                                        we proved le i i
                                        by (csubst0_getl_ge . . previous . . . H3 . H4)
getl i c0 (CHead e (Bind Abbr) u)
                                     end of h1
                                     (h2by (pr0_refl .) we proved pr0 t3 t3
                                     by (pr2_delta . . . . h1 . . h2 . H2)
                                     we proved pr2 c0 t3 t4
                                     by (pc3_pr2_r . . . previous)
pc3 c0 t3 t4
                                  end of h2
                                  by (pc3_pr2_u . . . h1 . h2)
                                  we proved pc3 c0 t2 t4
e:C.H4:(getl i c (CHead e (Bind Abbr) u)).(pc3 c0 t2 t4)
                      we proved e:C.(getl i c (CHead e (Bind Abbr) u))(pc3 c2 t2 t0)
i:nat.u:T.c2:C.t0:T.H1:(fsubst0 i u c t3 c2 t0).e:C.(getl i c (CHead e (Bind Abbr) u))(pc3 c2 t2 t0)
             case pr2_delta : c:C d:C u:T i:nat H0:getl i c (CHead d (Bind Abbr) u) t2:T t3:T H1:pr0 t2 t3 t0:T H2:subst0 i u t3 t0 
                the thesis becomes i0:nat.u0:T.c2:C.t4:T.H3:(fsubst0 i0 u0 c t0 c2 t4).e:C.(getl i0 c (CHead e (Bind Abbr) u0))(pc3 c2 t2 t4)
                    assume i0nat
                    assume u0T
                    assume c2C
                    assume t4T
                    suppose H3fsubst0 i0 u0 c t0 c2 t4
                      we proceed by induction on H3 to prove e:C.(getl i0 c (CHead e (Bind Abbr) u0))(pc3 c2 t2 t4)
                         case fsubst0_snd : t5:T H4:subst0 i0 u0 t0 t5 
                            the thesis becomes e:C.H5:(getl i0 c (CHead e (Bind Abbr) u0)).(pc3 c t2 t5)
                                assume eC
                                suppose H5getl i0 c (CHead e (Bind Abbr) u0)
                                  (h1
                                     by (pr2_free . . . H1)
                                     we proved pr2 c t2 t3
                                     by (pr3_pr2 . . . previous)
                                     we proved pr3 c t2 t3
                                     by (pc3_pr3_r . . . previous)
pc3 c t2 t3
                                  end of h1
                                  (h2
                                     (h1
                                        by (pr0_refl .)
                                        we proved pr0 t3 t3
                                        by (pr2_delta . . . . H0 . . previous . H2)
pr2 c t3 t0
                                     end of h1
                                     (h2
                                        by (pr0_refl .)
                                        we proved pr0 t0 t0
                                        by (pr2_delta . . . . H5 . . previous . H4)
                                        we proved pr2 c t0 t5
                                        by (pr3_pr2 . . . previous)
pr3 c t0 t5
                                     end of h2
                                     by (pr3_sing . . . h1 . h2)
                                     we proved pr3 c t3 t5
                                     by (pc3_pr3_r . . . previous)
pc3 c t3 t5
                                  end of h2
                                  by (pc3_t . . . h1 . h2)
                                  we proved pc3 c t2 t5
e:C.H5:(getl i0 c (CHead e (Bind Abbr) u0)).(pc3 c t2 t5)
                         case fsubst0_fst : c0:C H4:csubst0 i0 u0 c c0 
                            the thesis becomes e:C.H5:(getl i0 c (CHead e (Bind Abbr) u0)).(pc3 c0 t2 t0)
                                assume eC
                                suppose H5getl i0 c (CHead e (Bind Abbr) u0)
                                  (h1
                                     suppose H6lt i i0
                                        (H7
                                           by (csubst0_getl_lt . . H6 . . . H4 . H0)

                                              or4
                                                getl i c0 (CHead d (Bind Abbr) u)
                                                ex3_4
                                                  B
                                                  C
                                                  T
                                                  T
                                                  λb:B.λe0:C.λu:T.λ:T.eq C (CHead d (Bind Abbr) u) (CHead e0 (Bind b) u)
                                                  λb:B.λe0:C.λ:T.λw:T.getl i c0 (CHead e0 (Bind b) w)
                                                  λ:B.λ:C.λu:T.λw:T.subst0 (minus i0 (S i)) u0 u w
                                                ex3_4
                                                  B
                                                  C
                                                  C
                                                  T
                                                  λb:B.λe1:C.λ:C.λu:T.eq C (CHead d (Bind Abbr) u) (CHead e1 (Bind b) u)
                                                  λb:B.λ:C.λe2:C.λu:T.getl i c0 (CHead e2 (Bind b) u)
                                                  λ:B.λe1:C.λe2:C.λ:T.csubst0 (minus i0 (S i)) u0 e1 e2
                                                ex4_5
                                                  B
                                                  C
                                                  C
                                                  T
                                                  T
                                                  λb:B.λe1:C.λ:C.λu:T.λ:T.eq C (CHead d (Bind Abbr) u) (CHead e1 (Bind b) u)
                                                  λb:B.λ:C.λe2:C.λ:T.λw:T.getl i c0 (CHead e2 (Bind b) w)
                                                  λ:B.λ:C.λ:C.λu:T.λw:T.subst0 (minus i0 (S i)) u0 u w
                                                  λ:B.λe1:C.λe2:C.λ:T.λ:T.csubst0 (minus i0 (S i)) u0 e1 e2
                                        end of H7
                                        we proceed by induction on H7 to prove pc3 c0 t2 t0
                                           case or4_intro0 : H8:getl i c0 (CHead d (Bind Abbr) u) 
                                              the thesis becomes pc3 c0 t2 t0
                                                 by (pr2_delta . . . . H8 . . H1 . H2)
                                                 we proved pr2 c0 t2 t0
                                                 by (pc3_pr2_r . . . previous)
pc3 c0 t2 t0
                                           case or4_intro1 : H8:ex3_4 B C T T λb:B.λe0:C.λu1:T.λ:T.eq C (CHead d (Bind Abbr) u) (CHead e0 (Bind b) u1) λb:B.λe0:C.λ:T.λw:T.getl i c0 (CHead e0 (Bind b) w) λ:B.λ:C.λu1:T.λw:T.subst0 (minus i0 (S i)) u0 u1 w 
                                              the thesis becomes pc3 c0 t2 t0
                                                 we proceed by induction on H8 to prove pc3 c0 t2 t0
                                                    case ex3_4_intro : x0:B x1:C x2:T x3:T H9:eq C (CHead d (Bind Abbr) u) (CHead x1 (Bind x0) x2) H10:getl i c0 (CHead x1 (Bind x0) x3) H11:subst0 (minus i0 (S i)) u0 x2 x3 
                                                       the thesis becomes pc3 c0 t2 t0
                                                          (H12
                                                             by (f_equal . . . . . H9)
                                                             we proved 
                                                                eq
                                                                  C
                                                                  <λ:C.C> CASE CHead d (Bind Abbr) u OF CSort d | CHead c3  c3
                                                                  <λ:C.C> CASE CHead x1 (Bind x0) x2 OF CSort d | CHead c3  c3

                                                                eq
                                                                  C
                                                                  λe0:C.<λ:C.C> CASE e0 OF CSort d | CHead c3  c3 (CHead d (Bind Abbr) u)
                                                                  λe0:C.<λ:C.C> CASE e0 OF CSort d | CHead c3  c3 (CHead x1 (Bind x0) x2)
                                                          end of H12
                                                          (h1
                                                             (H13
                                                                by (f_equal . . . . . H9)
                                                                we proved 
                                                                   eq
                                                                     B
                                                                     <λ:C.B>
                                                                       CASE CHead d (Bind Abbr) u OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                     <λ:C.B>
                                                                       CASE CHead x1 (Bind x0) x2 OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr

                                                                   eq
                                                                     B
                                                                     λe0:C
                                                                         .<λ:C.B>
                                                                           CASE e0 OF
                                                                             CSort Abbr
                                                                           | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                       CHead d (Bind Abbr) u
                                                                     λe0:C
                                                                         .<λ:C.B>
                                                                           CASE e0 OF
                                                                             CSort Abbr
                                                                           | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                       CHead x1 (Bind x0) x2
                                                             end of H13
                                                             (h1
                                                                (H14
                                                                   by (f_equal . . . . . H9)
                                                                   we proved 
                                                                      eq
                                                                        T
                                                                        <λ:C.T> CASE CHead d (Bind Abbr) u OF CSort u | CHead   t5t5
                                                                        <λ:C.T> CASE CHead x1 (Bind x0) x2 OF CSort u | CHead   t5t5

                                                                      eq
                                                                        T
                                                                        λe0:C.<λ:C.T> CASE e0 OF CSort u | CHead   t5t5 (CHead d (Bind Abbr) u)
                                                                        λe0:C.<λ:C.T> CASE e0 OF CSort u | CHead   t5t5 (CHead x1 (Bind x0) x2)
                                                                end of H14
                                                                 suppose H15eq B Abbr x0
                                                                 suppose H16eq C d x1
                                                                   (H17
                                                                      consider H14
                                                                      we proved 
                                                                         eq
                                                                           T
                                                                           <λ:C.T> CASE CHead d (Bind Abbr) u OF CSort u | CHead   t5t5
                                                                           <λ:C.T> CASE CHead x1 (Bind x0) x2 OF CSort u | CHead   t5t5
                                                                      that is equivalent to eq T u x2
                                                                      by (eq_ind_r . . . H11 . previous)
subst0 (minus i0 (S i)) u0 u x3
                                                                   end of H17
                                                                   (H18
                                                                      by (eq_ind_r . . . H10 . H16)
getl i c0 (CHead d (Bind x0) x3)
                                                                   end of H18
                                                                   (H19
                                                                      by (eq_ind_r . . . H18 . H15)
getl i c0 (CHead d (Bind Abbr) x3)
                                                                   end of H19
                                                                   by (subst0_subst0_back . . . . H2 . . . H17)
                                                                   we proved ex2 T λt:T.subst0 i x3 t3 t λt:T.subst0 (S (plus (minus i0 (S i)) i)) u0 t0 t
                                                                   we proceed by induction on the previous result to prove pc3 c0 t2 t0
                                                                      case ex_intro2 : x:T H20:subst0 i x3 t3 x H21:subst0 (S (plus (minus i0 (S i)) i)) u0 t0 x 
                                                                         the thesis becomes pc3 c0 t2 t0
                                                                            (H22
                                                                               by (lt_plus_minus_r . . H6)
                                                                               we proved eq nat i0 (S (plus (minus i0 (S i)) i))
                                                                               by (eq_ind_r . . . H21 . previous)
subst0 i0 u0 t0 x
                                                                            end of H22
                                                                            (h1
                                                                               by (pr2_delta . . . . H19 . . H1 . H20)
pr2 c0 t2 x
                                                                            end of h1
                                                                            (h2
                                                                               (h1
                                                                                  by (le_n .)
                                                                                  we proved le i0 i0
                                                                                  by (csubst0_getl_ge . . previous . . . H4 . H5)
getl i0 c0 (CHead e (Bind Abbr) u0)
                                                                               end of h1
                                                                               (h2by (pr0_refl .) we proved pr0 t0 t0
                                                                               by (pr2_delta . . . . h1 . . h2 . H22)
                                                                               we proved pr2 c0 t0 x
                                                                               by (pc3_pr2_x . . . previous)
pc3 c0 x t0
                                                                            end of h2
                                                                            by (pc3_pr2_u . . . h1 . h2)
pc3 c0 t2 t0
                                                                   we proved pc3 c0 t2 t0
(eq B Abbr x0)(eq C d x1)(pc3 c0 t2 t0)
                                                             end of h1
                                                             (h2
                                                                consider H13
                                                                we proved 
                                                                   eq
                                                                     B
                                                                     <λ:C.B>
                                                                       CASE CHead d (Bind Abbr) u OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                     <λ:C.B>
                                                                       CASE CHead x1 (Bind x0) x2 OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
eq B Abbr x0
                                                             end of h2
                                                             by (h1 h2)
(eq C d x1)(pc3 c0 t2 t0)
                                                          end of h1
                                                          (h2
                                                             consider H12
                                                             we proved 
                                                                eq
                                                                  C
                                                                  <λ:C.C> CASE CHead d (Bind Abbr) u OF CSort d | CHead c3  c3
                                                                  <λ:C.C> CASE CHead x1 (Bind x0) x2 OF CSort d | CHead c3  c3
eq C d x1
                                                          end of h2
                                                          by (h1 h2)
pc3 c0 t2 t0
pc3 c0 t2 t0
                                           case or4_intro2 : H8:ex3_4 B C C T λb:B.λe1:C.λ:C.λu1:T.eq C (CHead d (Bind Abbr) u) (CHead e1 (Bind b) u1) λb:B.λ:C.λe2:C.λu1:T.getl i c0 (CHead e2 (Bind b) u1) λ:B.λe1:C.λe2:C.λ:T.csubst0 (minus i0 (S i)) u0 e1 e2 
                                              the thesis becomes pc3 c0 t2 t0
                                                 we proceed by induction on H8 to prove pc3 c0 t2 t0
                                                    case ex3_4_intro : x0:B x1:C x2:C x3:T H9:eq C (CHead d (Bind Abbr) u) (CHead x1 (Bind x0) x3) H10:getl i c0 (CHead x2 (Bind x0) x3) H11:csubst0 (minus i0 (S i)) u0 x1 x2 
                                                       the thesis becomes pc3 c0 t2 t0
                                                          (H12
                                                             by (f_equal . . . . . H9)
                                                             we proved 
                                                                eq
                                                                  C
                                                                  <λ:C.C> CASE CHead d (Bind Abbr) u OF CSort d | CHead c3  c3
                                                                  <λ:C.C> CASE CHead x1 (Bind x0) x3 OF CSort d | CHead c3  c3

                                                                eq
                                                                  C
                                                                  λe0:C.<λ:C.C> CASE e0 OF CSort d | CHead c3  c3 (CHead d (Bind Abbr) u)
                                                                  λe0:C.<λ:C.C> CASE e0 OF CSort d | CHead c3  c3 (CHead x1 (Bind x0) x3)
                                                          end of H12
                                                          (h1
                                                             (H13
                                                                by (f_equal . . . . . H9)
                                                                we proved 
                                                                   eq
                                                                     B
                                                                     <λ:C.B>
                                                                       CASE CHead d (Bind Abbr) u OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                     <λ:C.B>
                                                                       CASE CHead x1 (Bind x0) x3 OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr

                                                                   eq
                                                                     B
                                                                     λe0:C
                                                                         .<λ:C.B>
                                                                           CASE e0 OF
                                                                             CSort Abbr
                                                                           | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                       CHead d (Bind Abbr) u
                                                                     λe0:C
                                                                         .<λ:C.B>
                                                                           CASE e0 OF
                                                                             CSort Abbr
                                                                           | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                       CHead x1 (Bind x0) x3
                                                             end of H13
                                                             (h1
                                                                (H14
                                                                   by (f_equal . . . . . H9)
                                                                   we proved 
                                                                      eq
                                                                        T
                                                                        <λ:C.T> CASE CHead d (Bind Abbr) u OF CSort u | CHead   t5t5
                                                                        <λ:C.T> CASE CHead x1 (Bind x0) x3 OF CSort u | CHead   t5t5

                                                                      eq
                                                                        T
                                                                        λe0:C.<λ:C.T> CASE e0 OF CSort u | CHead   t5t5 (CHead d (Bind Abbr) u)
                                                                        λe0:C.<λ:C.T> CASE e0 OF CSort u | CHead   t5t5 (CHead x1 (Bind x0) x3)
                                                                end of H14
                                                                 suppose H15eq B Abbr x0
                                                                 suppose H16eq C d x1
                                                                   (H17
                                                                      consider H14
                                                                      we proved 
                                                                         eq
                                                                           T
                                                                           <λ:C.T> CASE CHead d (Bind Abbr) u OF CSort u | CHead   t5t5
                                                                           <λ:C.T> CASE CHead x1 (Bind x0) x3 OF CSort u | CHead   t5t5
                                                                      that is equivalent to eq T u x3
                                                                      by (eq_ind_r . . . H10 . previous)
getl i c0 (CHead x2 (Bind x0) u)
                                                                   end of H17
                                                                   (H19
                                                                      by (eq_ind_r . . . H17 . H15)
getl i c0 (CHead x2 (Bind Abbr) u)
                                                                   end of H19
                                                                   by (pr2_delta . . . . H19 . . H1 . H2)
                                                                   we proved pr2 c0 t2 t0
                                                                   by (pc3_pr2_r . . . previous)
                                                                   we proved pc3 c0 t2 t0
(eq B Abbr x0)(eq C d x1)(pc3 c0 t2 t0)
                                                             end of h1
                                                             (h2
                                                                consider H13
                                                                we proved 
                                                                   eq
                                                                     B
                                                                     <λ:C.B>
                                                                       CASE CHead d (Bind Abbr) u OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                     <λ:C.B>
                                                                       CASE CHead x1 (Bind x0) x3 OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
eq B Abbr x0
                                                             end of h2
                                                             by (h1 h2)
(eq C d x1)(pc3 c0 t2 t0)
                                                          end of h1
                                                          (h2
                                                             consider H12
                                                             we proved 
                                                                eq
                                                                  C
                                                                  <λ:C.C> CASE CHead d (Bind Abbr) u OF CSort d | CHead c3  c3
                                                                  <λ:C.C> CASE CHead x1 (Bind x0) x3 OF CSort d | CHead c3  c3
eq C d x1
                                                          end of h2
                                                          by (h1 h2)
pc3 c0 t2 t0
pc3 c0 t2 t0
                                           case or4_intro3 : H8:ex4_5 B C C T T λb:B.λe1:C.λ:C.λu1:T.λ:T.eq C (CHead d (Bind Abbr) u) (CHead e1 (Bind b) u1) λb:B.λ:C.λe2:C.λ:T.λw:T.getl i c0 (CHead e2 (Bind b) w) λ:B.λ:C.λ:C.λu1:T.λw:T.subst0 (minus i0 (S i)) u0 u1 w λ:B.λe1:C.λe2:C.λ:T.λ:T.csubst0 (minus i0 (S i)) u0 e1 e2 
                                              the thesis becomes pc3 c0 t2 t0
                                                 we proceed by induction on H8 to prove pc3 c0 t2 t0
                                                    case ex4_5_intro : x0:B x1:C x2:C x3:T x4:T H9:eq C (CHead d (Bind Abbr) u) (CHead x1 (Bind x0) x3) H10:getl i c0 (CHead x2 (Bind x0) x4) H11:subst0 (minus i0 (S i)) u0 x3 x4 H12:csubst0 (minus i0 (S i)) u0 x1 x2 
                                                       the thesis becomes pc3 c0 t2 t0
                                                          (H13
                                                             by (f_equal . . . . . H9)
                                                             we proved 
                                                                eq
                                                                  C
                                                                  <λ:C.C> CASE CHead d (Bind Abbr) u OF CSort d | CHead c3  c3
                                                                  <λ:C.C> CASE CHead x1 (Bind x0) x3 OF CSort d | CHead c3  c3

                                                                eq
                                                                  C
                                                                  λe0:C.<λ:C.C> CASE e0 OF CSort d | CHead c3  c3 (CHead d (Bind Abbr) u)
                                                                  λe0:C.<λ:C.C> CASE e0 OF CSort d | CHead c3  c3 (CHead x1 (Bind x0) x3)
                                                          end of H13
                                                          (h1
                                                             (H14
                                                                by (f_equal . . . . . H9)
                                                                we proved 
                                                                   eq
                                                                     B
                                                                     <λ:C.B>
                                                                       CASE CHead d (Bind Abbr) u OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                     <λ:C.B>
                                                                       CASE CHead x1 (Bind x0) x3 OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr

                                                                   eq
                                                                     B
                                                                     λe0:C
                                                                         .<λ:C.B>
                                                                           CASE e0 OF
                                                                             CSort Abbr
                                                                           | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                       CHead d (Bind Abbr) u
                                                                     λe0:C
                                                                         .<λ:C.B>
                                                                           CASE e0 OF
                                                                             CSort Abbr
                                                                           | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                       CHead x1 (Bind x0) x3
                                                             end of H14
                                                             (h1
                                                                (H15
                                                                   by (f_equal . . . . . H9)
                                                                   we proved 
                                                                      eq
                                                                        T
                                                                        <λ:C.T> CASE CHead d (Bind Abbr) u OF CSort u | CHead   t5t5
                                                                        <λ:C.T> CASE CHead x1 (Bind x0) x3 OF CSort u | CHead   t5t5

                                                                      eq
                                                                        T
                                                                        λe0:C.<λ:C.T> CASE e0 OF CSort u | CHead   t5t5 (CHead d (Bind Abbr) u)
                                                                        λe0:C.<λ:C.T> CASE e0 OF CSort u | CHead   t5t5 (CHead x1 (Bind x0) x3)
                                                                end of H15
                                                                 suppose H16eq B Abbr x0
                                                                 suppose H17eq C d x1
                                                                   (H18
                                                                      consider H15
                                                                      we proved 
                                                                         eq
                                                                           T
                                                                           <λ:C.T> CASE CHead d (Bind Abbr) u OF CSort u | CHead   t5t5
                                                                           <λ:C.T> CASE CHead x1 (Bind x0) x3 OF CSort u | CHead   t5t5
                                                                      that is equivalent to eq T u x3
                                                                      by (eq_ind_r . . . H11 . previous)
subst0 (minus i0 (S i)) u0 u x4
                                                                   end of H18
                                                                   (H20
                                                                      by (eq_ind_r . . . H10 . H16)
getl i c0 (CHead x2 (Bind Abbr) x4)
                                                                   end of H20
                                                                   by (subst0_subst0_back . . . . H2 . . . H18)
                                                                   we proved ex2 T λt:T.subst0 i x4 t3 t λt:T.subst0 (S (plus (minus i0 (S i)) i)) u0 t0 t
                                                                   we proceed by induction on the previous result to prove pc3 c0 t2 t0
                                                                      case ex_intro2 : x:T H21:subst0 i x4 t3 x H22:subst0 (S (plus (minus i0 (S i)) i)) u0 t0 x 
                                                                         the thesis becomes pc3 c0 t2 t0
                                                                            (H23
                                                                               by (lt_plus_minus_r . . H6)
                                                                               we proved eq nat i0 (S (plus (minus i0 (S i)) i))
                                                                               by (eq_ind_r . . . H22 . previous)
subst0 i0 u0 t0 x
                                                                            end of H23
                                                                            (h1
                                                                               by (pr2_delta . . . . H20 . . H1 . H21)
pr2 c0 t2 x
                                                                            end of h1
                                                                            (h2
                                                                               (h1
                                                                                  by (le_n .)
                                                                                  we proved le i0 i0
                                                                                  by (csubst0_getl_ge . . previous . . . H4 . H5)
getl i0 c0 (CHead e (Bind Abbr) u0)
                                                                               end of h1
                                                                               (h2by (pr0_refl .) we proved pr0 t0 t0
                                                                               by (pr2_delta . . . . h1 . . h2 . H23)
                                                                               we proved pr2 c0 t0 x
                                                                               by (pc3_pr2_x . . . previous)
pc3 c0 x t0
                                                                            end of h2
                                                                            by (pc3_pr2_u . . . h1 . h2)
pc3 c0 t2 t0
                                                                   we proved pc3 c0 t2 t0
(eq B Abbr x0)(eq C d x1)(pc3 c0 t2 t0)
                                                             end of h1
                                                             (h2
                                                                consider H14
                                                                we proved 
                                                                   eq
                                                                     B
                                                                     <λ:C.B>
                                                                       CASE CHead d (Bind Abbr) u OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                     <λ:C.B>
                                                                       CASE CHead x1 (Bind x0) x3 OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
eq B Abbr x0
                                                             end of h2
                                                             by (h1 h2)
(eq C d x1)(pc3 c0 t2 t0)
                                                          end of h1
                                                          (h2
                                                             consider H13
                                                             we proved 
                                                                eq
                                                                  C
                                                                  <λ:C.C> CASE CHead d (Bind Abbr) u OF CSort d | CHead c3  c3
                                                                  <λ:C.C> CASE CHead x1 (Bind x0) x3 OF CSort d | CHead c3  c3
eq C d x1
                                                          end of h2
                                                          by (h1 h2)
pc3 c0 t2 t0
pc3 c0 t2 t0
                                        we proved pc3 c0 t2 t0
(lt i i0)(pc3 c0 t2 t0)
                                  end of h1
                                  (h2
                                     suppose H6le i0 i
                                        by (csubst0_getl_ge . . H6 . . . H4 . H0)
                                        we proved getl i c0 (CHead d (Bind Abbr) u)
                                        by (pr2_delta . . . . previous . . H1 . H2)
                                        we proved pr2 c0 t2 t0
                                        by (pc3_pr2_r . . . previous)
                                        we proved pc3 c0 t2 t0
(le i0 i)(pc3 c0 t2 t0)
                                  end of h2
                                  by (lt_le_e . . . h1 h2)
                                  we proved pc3 c0 t2 t0
e:C.H5:(getl i0 c (CHead e (Bind Abbr) u0)).(pc3 c0 t2 t0)
                         case fsubst0_both : t5:T H4:subst0 i0 u0 t0 t5 c0:C H5:csubst0 i0 u0 c c0 
                            the thesis becomes e:C.H6:(getl i0 c (CHead e (Bind Abbr) u0)).(pc3 c0 t2 t5)
                                assume eC
                                suppose H6getl i0 c (CHead e (Bind Abbr) u0)
                                  (h1
                                     suppose H7lt i i0
                                        (H8
                                           by (csubst0_getl_lt . . H7 . . . H5 . H0)

                                              or4
                                                getl i c0 (CHead d (Bind Abbr) u)
                                                ex3_4
                                                  B
                                                  C
                                                  T
                                                  T
                                                  λb:B.λe0:C.λu:T.λ:T.eq C (CHead d (Bind Abbr) u) (CHead e0 (Bind b) u)
                                                  λb:B.λe0:C.λ:T.λw:T.getl i c0 (CHead e0 (Bind b) w)
                                                  λ:B.λ:C.λu:T.λw:T.subst0 (minus i0 (S i)) u0 u w
                                                ex3_4
                                                  B
                                                  C
                                                  C
                                                  T
                                                  λb:B.λe1:C.λ:C.λu:T.eq C (CHead d (Bind Abbr) u) (CHead e1 (Bind b) u)
                                                  λb:B.λ:C.λe2:C.λu:T.getl i c0 (CHead e2 (Bind b) u)
                                                  λ:B.λe1:C.λe2:C.λ:T.csubst0 (minus i0 (S i)) u0 e1 e2
                                                ex4_5
                                                  B
                                                  C
                                                  C
                                                  T
                                                  T
                                                  λb:B.λe1:C.λ:C.λu:T.λ:T.eq C (CHead d (Bind Abbr) u) (CHead e1 (Bind b) u)
                                                  λb:B.λ:C.λe2:C.λ:T.λw:T.getl i c0 (CHead e2 (Bind b) w)
                                                  λ:B.λ:C.λ:C.λu:T.λw:T.subst0 (minus i0 (S i)) u0 u w
                                                  λ:B.λe1:C.λe2:C.λ:T.λ:T.csubst0 (minus i0 (S i)) u0 e1 e2
                                        end of H8
                                        we proceed by induction on H8 to prove pc3 c0 t2 t5
                                           case or4_intro0 : H9:getl i c0 (CHead d (Bind Abbr) u) 
                                              the thesis becomes pc3 c0 t2 t5
                                                 (h1by (pr2_free . . . H1) we proved pr2 c0 t2 t3
                                                 (h2
                                                    (h1
                                                       by (pr0_refl .)
                                                       we proved pr0 t3 t3
                                                       by (pr2_delta . . . . H9 . . previous . H2)
pr2 c0 t3 t0
                                                    end of h1
                                                    (h2
                                                       (h1
                                                          by (le_n .)
                                                          we proved le i0 i0
                                                          by (csubst0_getl_ge . . previous . . . H5 . H6)
getl i0 c0 (CHead e (Bind Abbr) u0)
                                                       end of h1
                                                       (h2by (pr0_refl .) we proved pr0 t0 t0
                                                       by (pr2_delta . . . . h1 . . h2 . H4)
                                                       we proved pr2 c0 t0 t5
                                                       by (pr3_pr2 . . . previous)
pr3 c0 t0 t5
                                                    end of h2
                                                    by (pr3_sing . . . h1 . h2)
                                                    we proved pr3 c0 t3 t5
                                                    by (pc3_pr3_r . . . previous)
pc3 c0 t3 t5
                                                 end of h2
                                                 by (pc3_pr2_u . . . h1 . h2)
pc3 c0 t2 t5
                                           case or4_intro1 : H9:ex3_4 B C T T λb:B.λe0:C.λu1:T.λ:T.eq C (CHead d (Bind Abbr) u) (CHead e0 (Bind b) u1) λb:B.λe0:C.λ:T.λw:T.getl i c0 (CHead e0 (Bind b) w) λ:B.λ:C.λu1:T.λw:T.subst0 (minus i0 (S i)) u0 u1 w 
                                              the thesis becomes pc3 c0 t2 t5
                                                 we proceed by induction on H9 to prove pc3 c0 t2 t5
                                                    case ex3_4_intro : x0:B x1:C x2:T x3:T H10:eq C (CHead d (Bind Abbr) u) (CHead x1 (Bind x0) x2) H11:getl i c0 (CHead x1 (Bind x0) x3) H12:subst0 (minus i0 (S i)) u0 x2 x3 
                                                       the thesis becomes pc3 c0 t2 t5
                                                          (H13
                                                             by (f_equal . . . . . H10)
                                                             we proved 
                                                                eq
                                                                  C
                                                                  <λ:C.C> CASE CHead d (Bind Abbr) u OF CSort d | CHead c3  c3
                                                                  <λ:C.C> CASE CHead x1 (Bind x0) x2 OF CSort d | CHead c3  c3

                                                                eq
                                                                  C
                                                                  λe0:C.<λ:C.C> CASE e0 OF CSort d | CHead c3  c3 (CHead d (Bind Abbr) u)
                                                                  λe0:C.<λ:C.C> CASE e0 OF CSort d | CHead c3  c3 (CHead x1 (Bind x0) x2)
                                                          end of H13
                                                          (h1
                                                             (H14
                                                                by (f_equal . . . . . H10)
                                                                we proved 
                                                                   eq
                                                                     B
                                                                     <λ:C.B>
                                                                       CASE CHead d (Bind Abbr) u OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                     <λ:C.B>
                                                                       CASE CHead x1 (Bind x0) x2 OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr

                                                                   eq
                                                                     B
                                                                     λe0:C
                                                                         .<λ:C.B>
                                                                           CASE e0 OF
                                                                             CSort Abbr
                                                                           | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                       CHead d (Bind Abbr) u
                                                                     λe0:C
                                                                         .<λ:C.B>
                                                                           CASE e0 OF
                                                                             CSort Abbr
                                                                           | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                       CHead x1 (Bind x0) x2
                                                             end of H14
                                                             (h1
                                                                (H15
                                                                   by (f_equal . . . . . H10)
                                                                   we proved 
                                                                      eq
                                                                        T
                                                                        <λ:C.T> CASE CHead d (Bind Abbr) u OF CSort u | CHead   t6t6
                                                                        <λ:C.T> CASE CHead x1 (Bind x0) x2 OF CSort u | CHead   t6t6

                                                                      eq
                                                                        T
                                                                        λe0:C.<λ:C.T> CASE e0 OF CSort u | CHead   t6t6 (CHead d (Bind Abbr) u)
                                                                        λe0:C.<λ:C.T> CASE e0 OF CSort u | CHead   t6t6 (CHead x1 (Bind x0) x2)
                                                                end of H15
                                                                 suppose H16eq B Abbr x0
                                                                 suppose H17eq C d x1
                                                                   (H18
                                                                      consider H15
                                                                      we proved 
                                                                         eq
                                                                           T
                                                                           <λ:C.T> CASE CHead d (Bind Abbr) u OF CSort u | CHead   t6t6
                                                                           <λ:C.T> CASE CHead x1 (Bind x0) x2 OF CSort u | CHead   t6t6
                                                                      that is equivalent to eq T u x2
                                                                      by (eq_ind_r . . . H12 . previous)
subst0 (minus i0 (S i)) u0 u x3
                                                                   end of H18
                                                                   (H19
                                                                      by (eq_ind_r . . . H11 . H17)
getl i c0 (CHead d (Bind x0) x3)
                                                                   end of H19
                                                                   (H20
                                                                      by (eq_ind_r . . . H19 . H16)
getl i c0 (CHead d (Bind Abbr) x3)
                                                                   end of H20
                                                                   by (subst0_subst0_back . . . . H2 . . . H18)
                                                                   we proved ex2 T λt:T.subst0 i x3 t3 t λt:T.subst0 (S (plus (minus i0 (S i)) i)) u0 t0 t
                                                                   we proceed by induction on the previous result to prove pc3 c0 t2 t5
                                                                      case ex_intro2 : x:T H21:subst0 i x3 t3 x H22:subst0 (S (plus (minus i0 (S i)) i)) u0 t0 x 
                                                                         the thesis becomes pc3 c0 t2 t5
                                                                            (H23
                                                                               by (lt_plus_minus_r . . H7)
                                                                               we proved eq nat i0 (S (plus (minus i0 (S i)) i))
                                                                               by (eq_ind_r . . . H22 . previous)
subst0 i0 u0 t0 x
                                                                            end of H23
                                                                            (h1
                                                                               by (pr2_delta . . . . H20 . . H1 . H21)
pr2 c0 t2 x
                                                                            end of h1
                                                                            (h2
                                                                               (h1
                                                                                  (h1
                                                                                     by (le_n .)
                                                                                     we proved le i0 i0
                                                                                     by (csubst0_getl_ge . . previous . . . H5 . H6)
getl i0 c0 (CHead e (Bind Abbr) u0)
                                                                                  end of h1
                                                                                  (h2by (pr0_refl .) we proved pr0 t0 t0
                                                                                  by (pr2_delta . . . . h1 . . h2 . H23)
pr2 c0 t0 x
                                                                               end of h1
                                                                               (h2
                                                                                  (h1
                                                                                     by (le_n .)
                                                                                     we proved le i0 i0
                                                                                     by (csubst0_getl_ge . . previous . . . H5 . H6)
getl i0 c0 (CHead e (Bind Abbr) u0)
                                                                                  end of h1
                                                                                  (h2by (pr0_refl .) we proved pr0 t0 t0
                                                                                  by (pr2_delta . . . . h1 . . h2 . H4)
                                                                                  we proved pr2 c0 t0 t5
                                                                                  by (pc3_pr2_r . . . previous)
pc3 c0 t0 t5
                                                                               end of h2
                                                                               by (pc3_pr2_u2 . . . h1 . h2)
pc3 c0 x t5
                                                                            end of h2
                                                                            by (pc3_pr2_u . . . h1 . h2)
pc3 c0 t2 t5
                                                                   we proved pc3 c0 t2 t5
(eq B Abbr x0)(eq C d x1)(pc3 c0 t2 t5)
                                                             end of h1
                                                             (h2
                                                                consider H14
                                                                we proved 
                                                                   eq
                                                                     B
                                                                     <λ:C.B>
                                                                       CASE CHead d (Bind Abbr) u OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                     <λ:C.B>
                                                                       CASE CHead x1 (Bind x0) x2 OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
eq B Abbr x0
                                                             end of h2
                                                             by (h1 h2)
(eq C d x1)(pc3 c0 t2 t5)
                                                          end of h1
                                                          (h2
                                                             consider H13
                                                             we proved 
                                                                eq
                                                                  C
                                                                  <λ:C.C> CASE CHead d (Bind Abbr) u OF CSort d | CHead c3  c3
                                                                  <λ:C.C> CASE CHead x1 (Bind x0) x2 OF CSort d | CHead c3  c3
eq C d x1
                                                          end of h2
                                                          by (h1 h2)
pc3 c0 t2 t5
pc3 c0 t2 t5
                                           case or4_intro2 : H9:ex3_4 B C C T λb:B.λe1:C.λ:C.λu1:T.eq C (CHead d (Bind Abbr) u) (CHead e1 (Bind b) u1) λb:B.λ:C.λe2:C.λu1:T.getl i c0 (CHead e2 (Bind b) u1) λ:B.λe1:C.λe2:C.λ:T.csubst0 (minus i0 (S i)) u0 e1 e2 
                                              the thesis becomes pc3 c0 t2 t5
                                                 we proceed by induction on H9 to prove pc3 c0 t2 t5
                                                    case ex3_4_intro : x0:B x1:C x2:C x3:T H10:eq C (CHead d (Bind Abbr) u) (CHead x1 (Bind x0) x3) H11:getl i c0 (CHead x2 (Bind x0) x3) H12:csubst0 (minus i0 (S i)) u0 x1 x2 
                                                       the thesis becomes pc3 c0 t2 t5
                                                          (H13
                                                             by (f_equal . . . . . H10)
                                                             we proved 
                                                                eq
                                                                  C
                                                                  <λ:C.C> CASE CHead d (Bind Abbr) u OF CSort d | CHead c3  c3
                                                                  <λ:C.C> CASE CHead x1 (Bind x0) x3 OF CSort d | CHead c3  c3

                                                                eq
                                                                  C
                                                                  λe0:C.<λ:C.C> CASE e0 OF CSort d | CHead c3  c3 (CHead d (Bind Abbr) u)
                                                                  λe0:C.<λ:C.C> CASE e0 OF CSort d | CHead c3  c3 (CHead x1 (Bind x0) x3)
                                                          end of H13
                                                          (h1
                                                             (H14
                                                                by (f_equal . . . . . H10)
                                                                we proved 
                                                                   eq
                                                                     B
                                                                     <λ:C.B>
                                                                       CASE CHead d (Bind Abbr) u OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                     <λ:C.B>
                                                                       CASE CHead x1 (Bind x0) x3 OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr

                                                                   eq
                                                                     B
                                                                     λe0:C
                                                                         .<λ:C.B>
                                                                           CASE e0 OF
                                                                             CSort Abbr
                                                                           | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                       CHead d (Bind Abbr) u
                                                                     λe0:C
                                                                         .<λ:C.B>
                                                                           CASE e0 OF
                                                                             CSort Abbr
                                                                           | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                       CHead x1 (Bind x0) x3
                                                             end of H14
                                                             (h1
                                                                (H15
                                                                   by (f_equal . . . . . H10)
                                                                   we proved 
                                                                      eq
                                                                        T
                                                                        <λ:C.T> CASE CHead d (Bind Abbr) u OF CSort u | CHead   t6t6
                                                                        <λ:C.T> CASE CHead x1 (Bind x0) x3 OF CSort u | CHead   t6t6

                                                                      eq
                                                                        T
                                                                        λe0:C.<λ:C.T> CASE e0 OF CSort u | CHead   t6t6 (CHead d (Bind Abbr) u)
                                                                        λe0:C.<λ:C.T> CASE e0 OF CSort u | CHead   t6t6 (CHead x1 (Bind x0) x3)
                                                                end of H15
                                                                 suppose H16eq B Abbr x0
                                                                 suppose H17eq C d x1
                                                                   (H18
                                                                      consider H15
                                                                      we proved 
                                                                         eq
                                                                           T
                                                                           <λ:C.T> CASE CHead d (Bind Abbr) u OF CSort u | CHead   t6t6
                                                                           <λ:C.T> CASE CHead x1 (Bind x0) x3 OF CSort u | CHead   t6t6
                                                                      that is equivalent to eq T u x3
                                                                      by (eq_ind_r . . . H11 . previous)
getl i c0 (CHead x2 (Bind x0) u)
                                                                   end of H18
                                                                   (H20
                                                                      by (eq_ind_r . . . H18 . H16)
getl i c0 (CHead x2 (Bind Abbr) u)
                                                                   end of H20
                                                                   (h1
                                                                      by (pr2_delta . . . . H20 . . H1 . H2)
pr2 c0 t2 t0
                                                                   end of h1
                                                                   (h2
                                                                      (h1
                                                                         by (le_n .)
                                                                         we proved le i0 i0
                                                                         by (csubst0_getl_ge . . previous . . . H5 . H6)
getl i0 c0 (CHead e (Bind Abbr) u0)
                                                                      end of h1
                                                                      (h2by (pr0_refl .) we proved pr0 t0 t0
                                                                      by (pr2_delta . . . . h1 . . h2 . H4)
                                                                      we proved pr2 c0 t0 t5
                                                                      by (pc3_pr2_r . . . previous)
pc3 c0 t0 t5
                                                                   end of h2
                                                                   by (pc3_pr2_u . . . h1 . h2)
                                                                   we proved pc3 c0 t2 t5
(eq B Abbr x0)(eq C d x1)(pc3 c0 t2 t5)
                                                             end of h1
                                                             (h2
                                                                consider H14
                                                                we proved 
                                                                   eq
                                                                     B
                                                                     <λ:C.B>
                                                                       CASE CHead d (Bind Abbr) u OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                     <λ:C.B>
                                                                       CASE CHead x1 (Bind x0) x3 OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
eq B Abbr x0
                                                             end of h2
                                                             by (h1 h2)
(eq C d x1)(pc3 c0 t2 t5)
                                                          end of h1
                                                          (h2
                                                             consider H13
                                                             we proved 
                                                                eq
                                                                  C
                                                                  <λ:C.C> CASE CHead d (Bind Abbr) u OF CSort d | CHead c3  c3
                                                                  <λ:C.C> CASE CHead x1 (Bind x0) x3 OF CSort d | CHead c3  c3
eq C d x1
                                                          end of h2
                                                          by (h1 h2)
pc3 c0 t2 t5
pc3 c0 t2 t5
                                           case or4_intro3 : H9:ex4_5 B C C T T λb:B.λe1:C.λ:C.λu1:T.λ:T.eq C (CHead d (Bind Abbr) u) (CHead e1 (Bind b) u1) λb:B.λ:C.λe2:C.λ:T.λw:T.getl i c0 (CHead e2 (Bind b) w) λ:B.λ:C.λ:C.λu1:T.λw:T.subst0 (minus i0 (S i)) u0 u1 w λ:B.λe1:C.λe2:C.λ:T.λ:T.csubst0 (minus i0 (S i)) u0 e1 e2 
                                              the thesis becomes pc3 c0 t2 t5
                                                 we proceed by induction on H9 to prove pc3 c0 t2 t5
                                                    case ex4_5_intro : x0:B x1:C x2:C x3:T x4:T H10:eq C (CHead d (Bind Abbr) u) (CHead x1 (Bind x0) x3) H11:getl i c0 (CHead x2 (Bind x0) x4) H12:subst0 (minus i0 (S i)) u0 x3 x4 H13:csubst0 (minus i0 (S i)) u0 x1 x2 
                                                       the thesis becomes pc3 c0 t2 t5
                                                          (H14
                                                             by (f_equal . . . . . H10)
                                                             we proved 
                                                                eq
                                                                  C
                                                                  <λ:C.C> CASE CHead d (Bind Abbr) u OF CSort d | CHead c3  c3
                                                                  <λ:C.C> CASE CHead x1 (Bind x0) x3 OF CSort d | CHead c3  c3

                                                                eq
                                                                  C
                                                                  λe0:C.<λ:C.C> CASE e0 OF CSort d | CHead c3  c3 (CHead d (Bind Abbr) u)
                                                                  λe0:C.<λ:C.C> CASE e0 OF CSort d | CHead c3  c3 (CHead x1 (Bind x0) x3)
                                                          end of H14
                                                          (h1
                                                             (H15
                                                                by (f_equal . . . . . H10)
                                                                we proved 
                                                                   eq
                                                                     B
                                                                     <λ:C.B>
                                                                       CASE CHead d (Bind Abbr) u OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                     <λ:C.B>
                                                                       CASE CHead x1 (Bind x0) x3 OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr

                                                                   eq
                                                                     B
                                                                     λe0:C
                                                                         .<λ:C.B>
                                                                           CASE e0 OF
                                                                             CSort Abbr
                                                                           | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                       CHead d (Bind Abbr) u
                                                                     λe0:C
                                                                         .<λ:C.B>
                                                                           CASE e0 OF
                                                                             CSort Abbr
                                                                           | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                       CHead x1 (Bind x0) x3
                                                             end of H15
                                                             (h1
                                                                (H16
                                                                   by (f_equal . . . . . H10)
                                                                   we proved 
                                                                      eq
                                                                        T
                                                                        <λ:C.T> CASE CHead d (Bind Abbr) u OF CSort u | CHead   t6t6
                                                                        <λ:C.T> CASE CHead x1 (Bind x0) x3 OF CSort u | CHead   t6t6

                                                                      eq
                                                                        T
                                                                        λe0:C.<λ:C.T> CASE e0 OF CSort u | CHead   t6t6 (CHead d (Bind Abbr) u)
                                                                        λe0:C.<λ:C.T> CASE e0 OF CSort u | CHead   t6t6 (CHead x1 (Bind x0) x3)
                                                                end of H16
                                                                 suppose H17eq B Abbr x0
                                                                 suppose H18eq C d x1
                                                                   (H19
                                                                      consider H16
                                                                      we proved 
                                                                         eq
                                                                           T
                                                                           <λ:C.T> CASE CHead d (Bind Abbr) u OF CSort u | CHead   t6t6
                                                                           <λ:C.T> CASE CHead x1 (Bind x0) x3 OF CSort u | CHead   t6t6
                                                                      that is equivalent to eq T u x3
                                                                      by (eq_ind_r . . . H12 . previous)
subst0 (minus i0 (S i)) u0 u x4
                                                                   end of H19
                                                                   (H21
                                                                      by (eq_ind_r . . . H11 . H17)
getl i c0 (CHead x2 (Bind Abbr) x4)
                                                                   end of H21
                                                                   by (subst0_subst0_back . . . . H2 . . . H19)
                                                                   we proved ex2 T λt:T.subst0 i x4 t3 t λt:T.subst0 (S (plus (minus i0 (S i)) i)) u0 t0 t
                                                                   we proceed by induction on the previous result to prove pc3 c0 t2 t5
                                                                      case ex_intro2 : x:T H22:subst0 i x4 t3 x H23:subst0 (S (plus (minus i0 (S i)) i)) u0 t0 x 
                                                                         the thesis becomes pc3 c0 t2 t5
                                                                            (H24
                                                                               by (lt_plus_minus_r . . H7)
                                                                               we proved eq nat i0 (S (plus (minus i0 (S i)) i))
                                                                               by (eq_ind_r . . . H23 . previous)
subst0 i0 u0 t0 x
                                                                            end of H24
                                                                            (h1
                                                                               by (pr2_delta . . . . H21 . . H1 . H22)
pr2 c0 t2 x
                                                                            end of h1
                                                                            (h2
                                                                               (h1
                                                                                  (h1
                                                                                     by (le_n .)
                                                                                     we proved le i0 i0
                                                                                     by (csubst0_getl_ge . . previous . . . H5 . H6)
getl i0 c0 (CHead e (Bind Abbr) u0)
                                                                                  end of h1
                                                                                  (h2by (pr0_refl .) we proved pr0 t0 t0
                                                                                  by (pr2_delta . . . . h1 . . h2 . H24)
pr2 c0 t0 x
                                                                               end of h1
                                                                               (h2
                                                                                  (h1
                                                                                     by (le_n .)
                                                                                     we proved le i0 i0
                                                                                     by (csubst0_getl_ge . . previous . . . H5 . H6)
getl i0 c0 (CHead e (Bind Abbr) u0)
                                                                                  end of h1
                                                                                  (h2by (pr0_refl .) we proved pr0 t0 t0
                                                                                  by (pr2_delta . . . . h1 . . h2 . H4)
                                                                                  we proved pr2 c0 t0 t5
                                                                                  by (pc3_pr2_r . . . previous)
pc3 c0 t0 t5
                                                                               end of h2
                                                                               by (pc3_pr2_u2 . . . h1 . h2)
pc3 c0 x t5
                                                                            end of h2
                                                                            by (pc3_pr2_u . . . h1 . h2)
pc3 c0 t2 t5
                                                                   we proved pc3 c0 t2 t5
(eq B Abbr x0)(eq C d x1)(pc3 c0 t2 t5)
                                                             end of h1
                                                             (h2
                                                                consider H15
                                                                we proved 
                                                                   eq
                                                                     B
                                                                     <λ:C.B>
                                                                       CASE CHead d (Bind Abbr) u OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
                                                                     <λ:C.B>
                                                                       CASE CHead x1 (Bind x0) x3 OF
                                                                         CSort Abbr
                                                                       | CHead  k <λ:K.B> CASE k OF Bind bb | Flat Abbr
eq B Abbr x0
                                                             end of h2
                                                             by (h1 h2)
(eq C d x1)(pc3 c0 t2 t5)
                                                          end of h1
                                                          (h2
                                                             consider H14
                                                             we proved 
                                                                eq
                                                                  C
                                                                  <λ:C.C> CASE CHead d (Bind Abbr) u OF CSort d | CHead c3  c3
                                                                  <λ:C.C> CASE CHead x1 (Bind x0) x3 OF CSort d | CHead c3  c3
eq C d x1
                                                          end of h2
                                                          by (h1 h2)
pc3 c0 t2 t5
pc3 c0 t2 t5
                                        we proved pc3 c0 t2 t5
(lt i i0)(pc3 c0 t2 t5)
                                  end of h1
                                  (h2
                                     suppose H7le i0 i
                                        (h1
                                           by (csubst0_getl_ge . . H7 . . . H5 . H0)
                                           we proved getl i c0 (CHead d (Bind Abbr) u)
                                           by (pr2_delta . . . . previous . . H1 . H2)
pr2 c0 t2 t0
                                        end of h1
                                        (h2
                                           (h1
                                              by (le_n .)
                                              we proved le i0 i0
                                              by (csubst0_getl_ge . . previous . . . H5 . H6)
getl i0 c0 (CHead e (Bind Abbr) u0)
                                           end of h1
                                           (h2by (pr0_refl .) we proved pr0 t0 t0
                                           by (pr2_delta . . . . h1 . . h2 . H4)
                                           we proved pr2 c0 t0 t5
                                           by (pc3_pr2_r . . . previous)
pc3 c0 t0 t5
                                        end of h2
                                        by (pc3_pr2_u . . . h1 . h2)
                                        we proved pc3 c0 t2 t5
(le i0 i)(pc3 c0 t2 t5)
                                  end of h2
                                  by (lt_le_e . . . h1 h2)
                                  we proved pc3 c0 t2 t5
e:C.H6:(getl i0 c (CHead e (Bind Abbr) u0)).(pc3 c0 t2 t5)
                      we proved e:C.(getl i0 c (CHead e (Bind Abbr) u0))(pc3 c2 t2 t4)
i0:nat.u0:T.c2:C.t4:T.H3:(fsubst0 i0 u0 c t0 c2 t4).e:C.(getl i0 c (CHead e (Bind Abbr) u0))(pc3 c2 t2 t4)
          we proved 
             i:nat
               .u:T.c2:C.t3:T.(fsubst0 i u c1 t1 c2 t3)e:C.(getl i c1 (CHead e (Bind Abbr) u))(pc3 c2 t t3)
       we proved 
          c1:C
            .t:T
              .t1:T
                .pr2 c1 t t1
                  i:nat
                       .u:T.c2:C.t3:T.(fsubst0 i u c1 t1 c2 t3)e:C.(getl i c1 (CHead e (Bind Abbr) u))(pc3 c2 t t3)