DEFINITION arity_gen_abst()
TYPE =
       g:G
         .c:C
           .u:T
             .t:T
               .a:A
                 .arity g c (THead (Bind Abst) u t) a
                   (ex3_2
                        A
                        A
                        λa1:A.λa2:A.eq A a (AHead a1 a2)
                        λa1:A.λ:A.arity g c u (asucc g a1)
                        λ:A.λa2:A.arity g (CHead c (Bind Abst) u) t a2)
BODY =
        assume gG
        assume cC
        assume uT
        assume tT
        assume aA
        suppose Harity g c (THead (Bind Abst) u t) a
           assume yT
           suppose H0arity g c y a
             we proceed by induction on H0 to prove 
                eq T y (THead (Bind Abst) u t)
                  (ex3_2
                       A
                       A
                       λa1:A.λa2:A.eq A a (AHead a1 a2)
                       λa1:A.λ:A.arity g c u (asucc g a1)
                       λ:A.λa2:A.arity g (CHead c (Bind Abst) u) t a2)
                case arity_sort : c0:C n:nat 
                   the thesis becomes 
                   H1:eq T (TSort n) (THead (Bind Abst) u t)
                     .ex3_2
                       A
                       A
                       λa1:A.λa2:A.eq A (ASort O n) (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
                      suppose H1eq T (TSort n) (THead (Bind Abst) u t)
                         (H2
                            we proceed by induction on H1 to prove 
                               <λ:T.Prop>
                                 CASE THead (Bind Abst) u t OF
                                   TSort True
                                 | TLRef False
                                 | THead   False
                               case refl_equal : 
                                  the thesis becomes 
                                  <λ:T.Prop>
                                    CASE TSort n OF
                                      TSort True
                                    | TLRef False
                                    | THead   False
                                     consider I
                                     we proved True

                                        <λ:T.Prop>
                                          CASE TSort n OF
                                            TSort True
                                          | TLRef False
                                          | THead   False

                               <λ:T.Prop>
                                 CASE THead (Bind Abst) u t OF
                                   TSort True
                                 | TLRef False
                                 | THead   False
                         end of H2
                         consider H2
                         we proved 
                            <λ:T.Prop>
                              CASE THead (Bind Abst) u t OF
                                TSort True
                              | TLRef False
                              | THead   False
                         that is equivalent to False
                         we proceed by induction on the previous result to prove 
                            ex3_2
                              A
                              A
                              λa1:A.λa2:A.eq A (ASort O n) (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
                         we proved 
                            ex3_2
                              A
                              A
                              λa1:A.λa2:A.eq A (ASort O n) (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

                         H1:eq T (TSort n) (THead (Bind Abst) u t)
                           .ex3_2
                             A
                             A
                             λa1:A.λa2:A.eq A (ASort O n) (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
                case arity_abbr : c0:C d:C u0:T i:nat :getl i c0 (CHead d (Bind Abbr) u0) a0:A :arity g d u0 a0 
                   the thesis becomes 
                   H4:eq T (TLRef i) (THead (Bind Abst) u t)
                     .ex3_2
                       A
                       A
                       λa1:A.λa2:A.eq A a0 (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
                   () by induction hypothesis we know 
                      eq T u0 (THead (Bind Abst) u t)
                        (ex3_2
                             A
                             A
                             λa1:A.λa2:A.eq A a0 (AHead a1 a2)
                             λa1:A.λ:A.arity g d u (asucc g a1)
                             λ:A.λa2:A.arity g (CHead d (Bind Abst) u) t a2)
                      suppose H4eq T (TLRef i) (THead (Bind Abst) u t)
                         (H5
                            we proceed by induction on H4 to prove 
                               <λ:T.Prop>
                                 CASE THead (Bind Abst) u t OF
                                   TSort False
                                 | TLRef True
                                 | THead   False
                               case refl_equal : 
                                  the thesis becomes 
                                  <λ:T.Prop>
                                    CASE TLRef i OF
                                      TSort False
                                    | TLRef True
                                    | THead   False
                                     consider I
                                     we proved True

                                        <λ:T.Prop>
                                          CASE TLRef i OF
                                            TSort False
                                          | TLRef True
                                          | THead   False

                               <λ:T.Prop>
                                 CASE THead (Bind Abst) u t OF
                                   TSort False
                                 | TLRef True
                                 | THead   False
                         end of H5
                         consider H5
                         we proved 
                            <λ:T.Prop>
                              CASE THead (Bind Abst) u t OF
                                TSort False
                              | TLRef True
                              | THead   False
                         that is equivalent to False
                         we proceed by induction on the previous result to prove 
                            ex3_2
                              A
                              A
                              λa1:A.λa2:A.eq A a0 (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
                         we proved 
                            ex3_2
                              A
                              A
                              λa1:A.λa2:A.eq A a0 (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

                         H4:eq T (TLRef i) (THead (Bind Abst) u t)
                           .ex3_2
                             A
                             A
                             λa1:A.λa2:A.eq A a0 (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
                case arity_abst : c0:C d:C u0:T i:nat :getl i c0 (CHead d (Bind Abst) u0) a0:A :arity g d u0 (asucc g a0) 
                   the thesis becomes 
                   H4:eq T (TLRef i) (THead (Bind Abst) u t)
                     .ex3_2
                       A
                       A
                       λa1:A.λa2:A.eq A a0 (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
                   () by induction hypothesis we know 
                      eq T u0 (THead (Bind Abst) u t)
                        (ex3_2
                             A
                             A
                             λa1:A.λa2:A.eq A (asucc g a0) (AHead a1 a2)
                             λa1:A.λ:A.arity g d u (asucc g a1)
                             λ:A.λa2:A.arity g (CHead d (Bind Abst) u) t a2)
                      suppose H4eq T (TLRef i) (THead (Bind Abst) u t)
                         (H5
                            we proceed by induction on H4 to prove 
                               <λ:T.Prop>
                                 CASE THead (Bind Abst) u t OF
                                   TSort False
                                 | TLRef True
                                 | THead   False
                               case refl_equal : 
                                  the thesis becomes 
                                  <λ:T.Prop>
                                    CASE TLRef i OF
                                      TSort False
                                    | TLRef True
                                    | THead   False
                                     consider I
                                     we proved True

                                        <λ:T.Prop>
                                          CASE TLRef i OF
                                            TSort False
                                          | TLRef True
                                          | THead   False

                               <λ:T.Prop>
                                 CASE THead (Bind Abst) u t OF
                                   TSort False
                                 | TLRef True
                                 | THead   False
                         end of H5
                         consider H5
                         we proved 
                            <λ:T.Prop>
                              CASE THead (Bind Abst) u t OF
                                TSort False
                              | TLRef True
                              | THead   False
                         that is equivalent to False
                         we proceed by induction on the previous result to prove 
                            ex3_2
                              A
                              A
                              λa1:A.λa2:A.eq A a0 (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
                         we proved 
                            ex3_2
                              A
                              A
                              λa1:A.λa2:A.eq A a0 (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

                         H4:eq T (TLRef i) (THead (Bind Abst) u t)
                           .ex3_2
                             A
                             A
                             λa1:A.λa2:A.eq A a0 (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
                case arity_bind : b:B H1:not (eq B b Abst) c0:C u0:T a1:A H2:arity g c0 u0 a1 t0:T a2:A H4:arity g (CHead c0 (Bind b) u0) t0 a2 
                   the thesis becomes 
                   H6:eq T (THead (Bind b) u0 t0) (THead (Bind Abst) u t)
                     .ex3_2
                       A
                       A
                       λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                       λa3:A.λ:A.arity g c0 u (asucc g a3)
                       λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4
                   (H3) by induction hypothesis we know 
                      eq T u0 (THead (Bind Abst) u t)
                        (ex3_2
                             A
                             A
                             λa2:A.λa3:A.eq A a1 (AHead a2 a3)
                             λa2:A.λ:A.arity g c0 u (asucc g a2)
                             λ:A.λa3:A.arity g (CHead c0 (Bind Abst) u) t a3)
                   (H5) by induction hypothesis we know 
                      eq T t0 (THead (Bind Abst) u t)
                        (ex3_2
                             A
                             A
                             λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                             λa3:A.λ:A.arity g (CHead c0 (Bind b) u0) u (asucc g a3)
                             λ:A.λa4:A.arity g (CHead (CHead c0 (Bind b) u0) (Bind Abst) u) t a4)
                      suppose H6eq T (THead (Bind b) u0 t0) (THead (Bind Abst) u t)
                         (H7
                            by (f_equal . . . . . H6)
                            we proved 
                               eq
                                 B
                                 <λ:T.B>
                                   CASE THead (Bind b) u0 t0 OF
                                     TSort b
                                   | TLRef b
                                   | THead k  <λ:K.B> CASE k OF Bind b0b0 | Flat b
                                 <λ:T.B>
                                   CASE THead (Bind Abst) u t OF
                                     TSort b
                                   | TLRef b
                                   | THead k  <λ:K.B> CASE k OF Bind b0b0 | Flat b

                               eq
                                 B
                                 λe:T
                                     .<λ:T.B>
                                       CASE e OF
                                         TSort b
                                       | TLRef b
                                       | THead k  <λ:K.B> CASE k OF Bind b0b0 | Flat b
                                   THead (Bind b) u0 t0
                                 λe:T
                                     .<λ:T.B>
                                       CASE e OF
                                         TSort b
                                       | TLRef b
                                       | THead k  <λ:K.B> CASE k OF Bind b0b0 | Flat b
                                   THead (Bind Abst) u t
                         end of H7
                         (h1
                            (H8
                               by (f_equal . . . . . H6)
                               we proved 
                                  eq
                                    T
                                    <λ:T.T> CASE THead (Bind b) u0 t0 OF TSort u0 | TLRef u0 | THead  t1 t1
                                    <λ:T.T> CASE THead (Bind Abst) u t OF TSort u0 | TLRef u0 | THead  t1 t1

                                  eq
                                    T
                                    λe:T.<λ:T.T> CASE e OF TSort u0 | TLRef u0 | THead  t1 t1 (THead (Bind b) u0 t0)
                                    λe:T.<λ:T.T> CASE e OF TSort u0 | TLRef u0 | THead  t1 t1
                                      THead (Bind Abst) u t
                            end of H8
                            (h1
                               (H9
                                  by (f_equal . . . . . H6)
                                  we proved 
                                     eq
                                       T
                                       <λ:T.T> CASE THead (Bind b) u0 t0 OF TSort t0 | TLRef t0 | THead   t1t1
                                       <λ:T.T> CASE THead (Bind Abst) u t OF TSort t0 | TLRef t0 | THead   t1t1

                                     eq
                                       T
                                       λe:T.<λ:T.T> CASE e OF TSort t0 | TLRef t0 | THead   t1t1 (THead (Bind b) u0 t0)
                                       λe:T.<λ:T.T> CASE e OF TSort t0 | TLRef t0 | THead   t1t1
                                         THead (Bind Abst) u t
                               end of H9
                                suppose H10eq T u0 u
                                suppose H11eq B b Abst
                                  (H12
                                     consider H9
                                     we proved 
                                        eq
                                          T
                                          <λ:T.T> CASE THead (Bind b) u0 t0 OF TSort t0 | TLRef t0 | THead   t1t1
                                          <λ:T.T> CASE THead (Bind Abst) u t OF TSort t0 | TLRef t0 | THead   t1t1
                                     that is equivalent to eq T t0 t
                                     we proceed by induction on the previous result to prove 
                                        eq T t (THead (Bind Abst) u t)
                                          (ex3_2
                                               A
                                               A
                                               λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                                               λa3:A.λ:A.arity g (CHead c0 (Bind b) u0) u (asucc g a3)
                                               λ:A.λa4:A.arity g (CHead (CHead c0 (Bind b) u0) (Bind Abst) u) t a4)
                                        case refl_equal : 
                                           the thesis becomes the hypothesis H5

                                        eq T t (THead (Bind Abst) u t)
                                          (ex3_2
                                               A
                                               A
                                               λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                                               λa3:A.λ:A.arity g (CHead c0 (Bind b) u0) u (asucc g a3)
                                               λ:A.λa4:A.arity g (CHead (CHead c0 (Bind b) u0) (Bind Abst) u) t a4)
                                  end of H12
                                  (H13
                                     consider H9
                                     we proved 
                                        eq
                                          T
                                          <λ:T.T> CASE THead (Bind b) u0 t0 OF TSort t0 | TLRef t0 | THead   t1t1
                                          <λ:T.T> CASE THead (Bind Abst) u t OF TSort t0 | TLRef t0 | THead   t1t1
                                     that is equivalent to eq T t0 t
                                     we proceed by induction on the previous result to prove arity g (CHead c0 (Bind b) u0) t a2
                                        case refl_equal : 
                                           the thesis becomes the hypothesis H4
arity g (CHead c0 (Bind b) u0) t a2
                                  end of H13
                                  (H14
                                     we proceed by induction on H10 to prove 
                                        eq T t (THead (Bind Abst) u t)
                                          (ex3_2
                                               A
                                               A
                                               λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                                               λa3:A.λ:A.arity g (CHead c0 (Bind b) u) u (asucc g a3)
                                               λ:A.λa4:A.arity g (CHead (CHead c0 (Bind b) u) (Bind Abst) u) t a4)
                                        case refl_equal : 
                                           the thesis becomes the hypothesis H12

                                        eq T t (THead (Bind Abst) u t)
                                          (ex3_2
                                               A
                                               A
                                               λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                                               λa3:A.λ:A.arity g (CHead c0 (Bind b) u) u (asucc g a3)
                                               λ:A.λa4:A.arity g (CHead (CHead c0 (Bind b) u) (Bind Abst) u) t a4)
                                  end of H14
                                  (H15
                                     we proceed by induction on H10 to prove arity g (CHead c0 (Bind b) u) t a2
                                        case refl_equal : 
                                           the thesis becomes the hypothesis H13
arity g (CHead c0 (Bind b) u) t a2
                                  end of H15
                                  (H20
                                     we proceed by induction on H11 to prove not (eq B Abst Abst)
                                        case refl_equal : 
                                           the thesis becomes the hypothesis H1
not (eq B Abst Abst)
                                  end of H20
                                  (H21
                                     by (refl_equal . .)
                                     we proved eq B Abst Abst
                                     by (H20 previous)
                                     we proved False
                                     by cases on the previous result we prove 
                                        ex3_2
                                          A
                                          A
                                          λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                                          λa3:A.λ:A.arity g c0 u (asucc g a3)
                                          λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4

                                        ex3_2
                                          A
                                          A
                                          λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                                          λa3:A.λ:A.arity g c0 u (asucc g a3)
                                          λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4
                                  end of H21
                                  consider H21
                                  we proved 
                                     ex3_2
                                       A
                                       A
                                       λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                                       λa3:A.λ:A.arity g c0 u (asucc g a3)
                                       λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4

                                  eq T u0 u
                                    (eq B b Abst
                                         (ex3_2
                                              A
                                              A
                                              λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                                              λa3:A.λ:A.arity g c0 u (asucc g a3)
                                              λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4))
                            end of h1
                            (h2
                               consider H8
                               we proved 
                                  eq
                                    T
                                    <λ:T.T> CASE THead (Bind b) u0 t0 OF TSort u0 | TLRef u0 | THead  t1 t1
                                    <λ:T.T> CASE THead (Bind Abst) u t OF TSort u0 | TLRef u0 | THead  t1 t1
eq T u0 u
                            end of h2
                            by (h1 h2)

                               eq B b Abst
                                 (ex3_2
                                      A
                                      A
                                      λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                                      λa3:A.λ:A.arity g c0 u (asucc g a3)
                                      λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4)
                         end of h1
                         (h2
                            consider H7
                            we proved 
                               eq
                                 B
                                 <λ:T.B>
                                   CASE THead (Bind b) u0 t0 OF
                                     TSort b
                                   | TLRef b
                                   | THead k  <λ:K.B> CASE k OF Bind b0b0 | Flat b
                                 <λ:T.B>
                                   CASE THead (Bind Abst) u t OF
                                     TSort b
                                   | TLRef b
                                   | THead k  <λ:K.B> CASE k OF Bind b0b0 | Flat b
eq B b Abst
                         end of h2
                         by (h1 h2)
                         we proved 
                            ex3_2
                              A
                              A
                              λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                              λa3:A.λ:A.arity g c0 u (asucc g a3)
                              λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4

                         H6:eq T (THead (Bind b) u0 t0) (THead (Bind Abst) u t)
                           .ex3_2
                             A
                             A
                             λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                             λa3:A.λ:A.arity g c0 u (asucc g a3)
                             λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4
                case arity_head : c0:C u0:T a1:A H1:arity g c0 u0 (asucc g a1) t0:T a2:A H3:arity g (CHead c0 (Bind Abst) u0) t0 a2 
                   the thesis becomes 
                   H5:eq T (THead (Bind Abst) u0 t0) (THead (Bind Abst) u t)
                     .ex3_2
                       A
                       A
                       λa3:A.λa4:A.eq A (AHead a1 a2) (AHead a3 a4)
                       λa3:A.λ:A.arity g c0 u (asucc g a3)
                       λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4
                   (H2) by induction hypothesis we know 
                      eq T u0 (THead (Bind Abst) u t)
                        (ex3_2
                             A
                             A
                             λa2:A.λa3:A.eq A (asucc g a1) (AHead a2 a3)
                             λa2:A.λ:A.arity g c0 u (asucc g a2)
                             λ:A.λa3:A.arity g (CHead c0 (Bind Abst) u) t a3)
                   (H4) by induction hypothesis we know 
                      eq T t0 (THead (Bind Abst) u t)
                        (ex3_2
                             A
                             A
                             λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                             λa3:A.λ:A.arity g (CHead c0 (Bind Abst) u0) u (asucc g a3)
                             λ:A.λa4:A.arity g (CHead (CHead c0 (Bind Abst) u0) (Bind Abst) u) t a4)
                      suppose H5eq T (THead (Bind Abst) u0 t0) (THead (Bind Abst) u t)
                         (H6
                            by (f_equal . . . . . H5)
                            we proved 
                               eq
                                 T
                                 <λ:T.T> CASE THead (Bind Abst) u0 t0 OF TSort u0 | TLRef u0 | THead  t1 t1
                                 <λ:T.T> CASE THead (Bind Abst) u t OF TSort u0 | TLRef u0 | THead  t1 t1

                               eq
                                 T
                                 λe:T.<λ:T.T> CASE e OF TSort u0 | TLRef u0 | THead  t1 t1
                                   THead (Bind Abst) u0 t0
                                 λe:T.<λ:T.T> CASE e OF TSort u0 | TLRef u0 | THead  t1 t1
                                   THead (Bind Abst) u t
                         end of H6
                         (h1
                            (H7
                               by (f_equal . . . . . H5)
                               we proved 
                                  eq
                                    T
                                    <λ:T.T> CASE THead (Bind Abst) u0 t0 OF TSort t0 | TLRef t0 | THead   t1t1
                                    <λ:T.T> CASE THead (Bind Abst) u t OF TSort t0 | TLRef t0 | THead   t1t1

                                  eq
                                    T
                                    λe:T.<λ:T.T> CASE e OF TSort t0 | TLRef t0 | THead   t1t1
                                      THead (Bind Abst) u0 t0
                                    λe:T.<λ:T.T> CASE e OF TSort t0 | TLRef t0 | THead   t1t1
                                      THead (Bind Abst) u t
                            end of H7
                            suppose H8eq T u0 u
                               (H9
                                  consider H7
                                  we proved 
                                     eq
                                       T
                                       <λ:T.T> CASE THead (Bind Abst) u0 t0 OF TSort t0 | TLRef t0 | THead   t1t1
                                       <λ:T.T> CASE THead (Bind Abst) u t OF TSort t0 | TLRef t0 | THead   t1t1
                                  that is equivalent to eq T t0 t
                                  we proceed by induction on the previous result to prove 
                                     eq T t (THead (Bind Abst) u t)
                                       (ex3_2
                                            A
                                            A
                                            λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                                            λa3:A.λ:A.arity g (CHead c0 (Bind Abst) u0) u (asucc g a3)
                                            λ:A.λa4:A.arity g (CHead (CHead c0 (Bind Abst) u0) (Bind Abst) u) t a4)
                                     case refl_equal : 
                                        the thesis becomes the hypothesis H4

                                     eq T t (THead (Bind Abst) u t)
                                       (ex3_2
                                            A
                                            A
                                            λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                                            λa3:A.λ:A.arity g (CHead c0 (Bind Abst) u0) u (asucc g a3)
                                            λ:A.λa4:A.arity g (CHead (CHead c0 (Bind Abst) u0) (Bind Abst) u) t a4)
                               end of H9
                               (H10
                                  consider H7
                                  we proved 
                                     eq
                                       T
                                       <λ:T.T> CASE THead (Bind Abst) u0 t0 OF TSort t0 | TLRef t0 | THead   t1t1
                                       <λ:T.T> CASE THead (Bind Abst) u t OF TSort t0 | TLRef t0 | THead   t1t1
                                  that is equivalent to eq T t0 t
                                  we proceed by induction on the previous result to prove arity g (CHead c0 (Bind Abst) u0) t a2
                                     case refl_equal : 
                                        the thesis becomes the hypothesis H3
arity g (CHead c0 (Bind Abst) u0) t a2
                               end of H10
                               (H12
                                  we proceed by induction on H8 to prove arity g (CHead c0 (Bind Abst) u) t a2
                                     case refl_equal : 
                                        the thesis becomes the hypothesis H10
arity g (CHead c0 (Bind Abst) u) t a2
                               end of H12
                               (H14
                                  we proceed by induction on H8 to prove arity g c0 u (asucc g a1)
                                     case refl_equal : 
                                        the thesis becomes the hypothesis H1
arity g c0 u (asucc g a1)
                               end of H14
                               by (refl_equal . .)
                               we proved eq A (AHead a1 a2) (AHead a1 a2)
                               by (ex3_2_intro . . . . . . . previous H14 H12)
                               we proved 
                                  ex3_2
                                    A
                                    A
                                    λa3:A.λa4:A.eq A (AHead a1 a2) (AHead a3 a4)
                                    λa3:A.λ:A.arity g c0 u (asucc g a3)
                                    λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4

                               eq T u0 u
                                 (ex3_2
                                      A
                                      A
                                      λa3:A.λa4:A.eq A (AHead a1 a2) (AHead a3 a4)
                                      λa3:A.λ:A.arity g c0 u (asucc g a3)
                                      λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4)
                         end of h1
                         (h2
                            consider H6
                            we proved 
                               eq
                                 T
                                 <λ:T.T> CASE THead (Bind Abst) u0 t0 OF TSort u0 | TLRef u0 | THead  t1 t1
                                 <λ:T.T> CASE THead (Bind Abst) u t OF TSort u0 | TLRef u0 | THead  t1 t1
eq T u0 u
                         end of h2
                         by (h1 h2)
                         we proved 
                            ex3_2
                              A
                              A
                              λa3:A.λa4:A.eq A (AHead a1 a2) (AHead a3 a4)
                              λa3:A.λ:A.arity g c0 u (asucc g a3)
                              λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4

                         H5:eq T (THead (Bind Abst) u0 t0) (THead (Bind Abst) u t)
                           .ex3_2
                             A
                             A
                             λa3:A.λa4:A.eq A (AHead a1 a2) (AHead a3 a4)
                             λa3:A.λ:A.arity g c0 u (asucc g a3)
                             λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4
                case arity_appl : c0:C u0:T a1:A :arity g c0 u0 a1 t0:T a2:A :arity g c0 t0 (AHead a1 a2) 
                   the thesis becomes 
                   H5:eq T (THead (Flat Appl) u0 t0) (THead (Bind Abst) u t)
                     .ex3_2
                       A
                       A
                       λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                       λa3:A.λ:A.arity g c0 u (asucc g a3)
                       λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4
                   () by induction hypothesis we know 
                      eq T u0 (THead (Bind Abst) u t)
                        (ex3_2
                             A
                             A
                             λa2:A.λa3:A.eq A a1 (AHead a2 a3)
                             λa2:A.λ:A.arity g c0 u (asucc g a2)
                             λ:A.λa3:A.arity g (CHead c0 (Bind Abst) u) t a3)
                   () by induction hypothesis we know 
                      eq T t0 (THead (Bind Abst) u t)
                        (ex3_2
                             A
                             A
                             λa3:A.λa4:A.eq A (AHead a1 a2) (AHead a3 a4)
                             λa3:A.λ:A.arity g c0 u (asucc g a3)
                             λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4)
                      suppose H5eq T (THead (Flat Appl) u0 t0) (THead (Bind Abst) u t)
                         (H6
                            we proceed by induction on H5 to prove 
                               <λ:T.Prop>
                                 CASE THead (Bind Abst) u t OF
                                   TSort False
                                 | TLRef False
                                 | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True
                               case refl_equal : 
                                  the thesis becomes 
                                  <λ:T.Prop>
                                    CASE THead (Flat Appl) u0 t0 OF
                                      TSort False
                                    | TLRef False
                                    | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True
                                     consider I
                                     we proved True

                                        <λ:T.Prop>
                                          CASE THead (Flat Appl) u0 t0 OF
                                            TSort False
                                          | TLRef False
                                          | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True

                               <λ:T.Prop>
                                 CASE THead (Bind Abst) u t OF
                                   TSort False
                                 | TLRef False
                                 | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True
                         end of H6
                         consider H6
                         we proved 
                            <λ:T.Prop>
                              CASE THead (Bind Abst) u t OF
                                TSort False
                              | TLRef False
                              | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True
                         that is equivalent to False
                         we proceed by induction on the previous result to prove 
                            ex3_2
                              A
                              A
                              λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                              λa3:A.λ:A.arity g c0 u (asucc g a3)
                              λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4
                         we proved 
                            ex3_2
                              A
                              A
                              λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                              λa3:A.λ:A.arity g c0 u (asucc g a3)
                              λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4

                         H5:eq T (THead (Flat Appl) u0 t0) (THead (Bind Abst) u t)
                           .ex3_2
                             A
                             A
                             λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                             λa3:A.λ:A.arity g c0 u (asucc g a3)
                             λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4
                case arity_cast : c0:C u0:T a0:A :arity g c0 u0 (asucc g a0) t0:T :arity g c0 t0 a0 
                   the thesis becomes 
                   H5:eq T (THead (Flat Cast) u0 t0) (THead (Bind Abst) u t)
                     .ex3_2
                       A
                       A
                       λa1:A.λa2:A.eq A a0 (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
                   () by induction hypothesis we know 
                      eq T u0 (THead (Bind Abst) u t)
                        (ex3_2
                             A
                             A
                             λa1:A.λa2:A.eq A (asucc g a0) (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)
                   () by induction hypothesis we know 
                      eq T t0 (THead (Bind Abst) u t)
                        (ex3_2
                             A
                             A
                             λa1:A.λa2:A.eq A a0 (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)
                      suppose H5eq T (THead (Flat Cast) u0 t0) (THead (Bind Abst) u t)
                         (H6
                            we proceed by induction on H5 to prove 
                               <λ:T.Prop>
                                 CASE THead (Bind Abst) u t OF
                                   TSort False
                                 | TLRef False
                                 | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True
                               case refl_equal : 
                                  the thesis becomes 
                                  <λ:T.Prop>
                                    CASE THead (Flat Cast) u0 t0 OF
                                      TSort False
                                    | TLRef False
                                    | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True
                                     consider I
                                     we proved True

                                        <λ:T.Prop>
                                          CASE THead (Flat Cast) u0 t0 OF
                                            TSort False
                                          | TLRef False
                                          | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True

                               <λ:T.Prop>
                                 CASE THead (Bind Abst) u t OF
                                   TSort False
                                 | TLRef False
                                 | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True
                         end of H6
                         consider H6
                         we proved 
                            <λ:T.Prop>
                              CASE THead (Bind Abst) u t OF
                                TSort False
                              | TLRef False
                              | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True
                         that is equivalent to False
                         we proceed by induction on the previous result to prove 
                            ex3_2
                              A
                              A
                              λa1:A.λa2:A.eq A a0 (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
                         we proved 
                            ex3_2
                              A
                              A
                              λa1:A.λa2:A.eq A a0 (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

                         H5:eq T (THead (Flat Cast) u0 t0) (THead (Bind Abst) u t)
                           .ex3_2
                             A
                             A
                             λa1:A.λa2:A.eq A a0 (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
                case arity_repl : c0:C t0:T a1:A H1:arity g c0 t0 a1 a2:A H3:leq g a1 a2 
                   the thesis becomes 
                   H4:eq T t0 (THead (Bind Abst) u t)
                     .ex3_2
                       A
                       A
                       λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                       λa3:A.λ:A.arity g c0 u (asucc g a3)
                       λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4
                   (H2) by induction hypothesis we know 
                      eq T t0 (THead (Bind Abst) u t)
                        (ex3_2
                             A
                             A
                             λa2:A.λa3:A.eq A a1 (AHead a2 a3)
                             λa2:A.λ:A.arity g c0 u (asucc g a2)
                             λ:A.λa3:A.arity g (CHead c0 (Bind Abst) u) t a3)
                      suppose H4eq T t0 (THead (Bind Abst) u t)
                         (H5
                            by (f_equal . . . . . H4)
                            we proved eq T t0 (THead (Bind Abst) u t)
eq T (λe:T.e t0) (λe:T.e (THead (Bind Abst) u t))
                         end of H5
                         (H6
                            we proceed by induction on H5 to prove 
                               eq T (THead (Bind Abst) u t) (THead (Bind Abst) u t)
                                 (ex3_2
                                      A
                                      A
                                      λa3:A.λa4:A.eq A a1 (AHead a3 a4)
                                      λa3:A.λ:A.arity g c0 u (asucc g a3)
                                      λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4)
                               case refl_equal : 
                                  the thesis becomes the hypothesis H2

                               eq T (THead (Bind Abst) u t) (THead (Bind Abst) u t)
                                 (ex3_2
                                      A
                                      A
                                      λa3:A.λa4:A.eq A a1 (AHead a3 a4)
                                      λa3:A.λ:A.arity g c0 u (asucc g a3)
                                      λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4)
                         end of H6
                         (H7
                            we proceed by induction on H5 to prove arity g c0 (THead (Bind Abst) u t) a1
                               case refl_equal : 
                                  the thesis becomes the hypothesis H1
arity g c0 (THead (Bind Abst) u t) a1
                         end of H7
                         (H8
                            by (refl_equal . .)
                            we proved eq T (THead (Bind Abst) u t) (THead (Bind Abst) u t)
                            by (H6 previous)

                               ex3_2
                                 A
                                 A
                                 λa3:A.λa4:A.eq A a1 (AHead a3 a4)
                                 λa3:A.λ:A.arity g c0 u (asucc g a3)
                                 λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4
                         end of H8
                         we proceed by induction on H8 to prove 
                            ex3_2
                              A
                              A
                              λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                              λa3:A.λ:A.arity g c0 u (asucc g a3)
                              λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4
                            case ex3_2_intro : x0:A x1:A H9:eq A a1 (AHead x0 x1) H10:arity g c0 u (asucc g x0) H11:arity g (CHead c0 (Bind Abst) u) t x1 
                               the thesis becomes 
                               ex3_2
                                 A
                                 A
                                 λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                                 λa3:A.λ:A.arity g c0 u (asucc g a3)
                                 λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4
                                  (H12
                                     we proceed by induction on H9 to prove leq g (AHead x0 x1) a2
                                        case refl_equal : 
                                           the thesis becomes the hypothesis H3
leq g (AHead x0 x1) a2
                                  end of H12
                                  (H_x
                                     by (leq_gen_head1 . . . . H12)
ex3_2 A A λa3:A.λ:A.leq g x0 a3 λ:A.λa4:A.leq g x1 a4 λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                                  end of H_x
                                  (H14consider H_x
                                  we proceed by induction on H14 to prove 
                                     ex3_2
                                       A
                                       A
                                       λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                                       λa3:A.λ:A.arity g c0 u (asucc g a3)
                                       λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4
                                     case ex3_2_intro : x2:A x3:A H15:leq g x0 x2 H16:leq g x1 x3 H17:eq A a2 (AHead x2 x3) 
                                        the thesis becomes 
                                        ex3_2
                                          A
                                          A
                                          λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                                          λa3:A.λ:A.arity g c0 u (asucc g a3)
                                          λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4
                                           (H18
                                              by (f_equal . . . . . H17)
                                              we proved eq A a2 (AHead x2 x3)
eq A (λe:A.e a2) (λe:A.e (AHead x2 x3))
                                           end of H18
                                           (h1
                                              by (refl_equal . .)
eq A (AHead x2 x3) (AHead x2 x3)
                                           end of h1
                                           (h2
                                              by (asucc_repl . . . H15)
                                              we proved leq g (asucc g x0) (asucc g x2)
                                              by (arity_repl . . . . H10 . previous)
arity g c0 u (asucc g x2)
                                           end of h2
                                           (h3
                                              by (arity_repl . . . . H11 . H16)
arity g (CHead c0 (Bind Abst) u) t x3
                                           end of h3
                                           by (ex3_2_intro . . . . . . . h1 h2 h3)
                                           we proved 
                                              ex3_2
                                                A
                                                A
                                                λa3:A.λa4:A.eq A (AHead x2 x3) (AHead a3 a4)
                                                λa3:A.λ:A.arity g c0 u (asucc g a3)
                                                λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4
                                           by (eq_ind_r . . . previous . H18)

                                              ex3_2
                                                A
                                                A
                                                λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                                                λa3:A.λ:A.arity g c0 u (asucc g a3)
                                                λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4

                                     ex3_2
                                       A
                                       A
                                       λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                                       λa3:A.λ:A.arity g c0 u (asucc g a3)
                                       λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4
                         we proved 
                            ex3_2
                              A
                              A
                              λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                              λa3:A.λ:A.arity g c0 u (asucc g a3)
                              λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4

                         H4:eq T t0 (THead (Bind Abst) u t)
                           .ex3_2
                             A
                             A
                             λa3:A.λa4:A.eq A a2 (AHead a3 a4)
                             λa3:A.λ:A.arity g c0 u (asucc g a3)
                             λ:A.λa4:A.arity g (CHead c0 (Bind Abst) u) t a4
             we proved 
                eq T y (THead (Bind Abst) u t)
                  (ex3_2
                       A
                       A
                       λa1:A.λa2:A.eq A a (AHead a1 a2)
                       λa1:A.λ:A.arity g c u (asucc g a1)
                       λ:A.λa2:A.arity g (CHead c (Bind Abst) u) t a2)
          we proved 
             y:T
               .arity g c y a
                 (eq T y (THead (Bind Abst) u t)
                      (ex3_2
                           A
                           A
                           λa1:A.λa2:A.eq A a (AHead a1 a2)
                           λa1:A.λ:A.arity g c u (asucc g a1)
                           λ:A.λa2:A.arity g (CHead c (Bind Abst) u) t a2))
          by (insert_eq . . . . previous H)
          we proved 
             ex3_2
               A
               A
               λa1:A.λa2:A.eq A a (AHead a1 a2)
               λa1:A.λ:A.arity g c u (asucc g a1)
               λ:A.λa2:A.arity g (CHead c (Bind Abst) u) t a2
       we proved 
          g:G
            .c:C
              .u:T
                .t:T
                  .a:A
                    .arity g c (THead (Bind Abst) u t) a
                      (ex3_2
                           A
                           A
                           λa1:A.λa2:A.eq A a (AHead a1 a2)
                           λa1:A.λ:A.arity g c u (asucc g a1)
                           λ:A.λa2:A.arity g (CHead c (Bind Abst) u) t a2)