DEFINITION arity_gen_lref()
TYPE =
       g:G
         .c:C
           .i:nat
             .a:A
               .arity g c (TLRef i) a
                 (or
                      ex2_2 C T λd:C.λu:T.getl i c (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a
                      ex2_2
                        C
                        T
                        λd:C.λu:T.getl i c (CHead d (Bind Abst) u)
                        λd:C.λu:T.arity g d u (asucc g a))
BODY =
        assume gG
        assume cC
        assume inat
        assume aA
        suppose Harity g c (TLRef i) a
           assume yT
           suppose H0arity g c y a
             we proceed by induction on H0 to prove 
                eq T y (TLRef i)
                  (or
                       ex2_2 C T λd:C.λu:T.getl i c (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a
                       ex2_2
                         C
                         T
                         λd:C.λu:T.getl i c (CHead d (Bind Abst) u)
                         λd:C.λu:T.arity g d u (asucc g a))
                case arity_sort : c0:C n:nat 
                   the thesis becomes 
                   H1:eq T (TSort n) (TLRef i)
                     .or
                       ex2_2
                         C
                         T
                         λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u)
                         λd:C.λu:T.arity g d u (ASort O n)
                       ex2_2
                         C
                         T
                         λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                         λd:C.λu:T.arity g d u (asucc g (ASort O n))
                      suppose H1eq T (TSort n) (TLRef i)
                         (H2
                            we proceed by induction on H1 to prove 
                               <λ:T.Prop>
                                 CASE TLRef i 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 TLRef i OF
                                   TSort True
                                 | TLRef False
                                 | THead   False
                         end of H2
                         consider H2
                         we proved 
                            <λ:T.Prop>
                              CASE TLRef i OF
                                TSort True
                              | TLRef False
                              | THead   False
                         that is equivalent to False
                         we proceed by induction on the previous result to prove 
                            or
                              ex2_2
                                C
                                T
                                λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u)
                                λd:C.λu:T.arity g d u (ASort O n)
                              ex2_2
                                C
                                T
                                λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                                λd:C.λu:T.arity g d u (asucc g (ASort O n))
                         we proved 
                            or
                              ex2_2
                                C
                                T
                                λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u)
                                λd:C.λu:T.arity g d u (ASort O n)
                              ex2_2
                                C
                                T
                                λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                                λd:C.λu:T.arity g d u (asucc g (ASort O n))

                         H1:eq T (TSort n) (TLRef i)
                           .or
                             ex2_2
                               C
                               T
                               λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u)
                               λd:C.λu:T.arity g d u (ASort O n)
                             ex2_2
                               C
                               T
                               λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                               λd:C.λu:T.arity g d u (asucc g (ASort O n))
                case arity_abbr : c0:C d:C u:T i0:nat H1:getl i0 c0 (CHead d (Bind Abbr) u) a0:A H2:arity g d u a0 
                   the thesis becomes 
                   H4:eq T (TLRef i0) (TLRef i)
                     .or
                       ex2_2 C T λd0:C.λu0:T.getl i c0 (CHead d0 (Bind Abbr) u0) λd0:C.λu0:T.arity g d0 u0 a0
                       ex2_2 C T λd0:C.λu0:T.getl i c0 (CHead d0 (Bind Abst) u0) λd0:C.λu0:T.arity g d0 u0 (asucc g a0)
                   () by induction hypothesis we know 
                      eq T u (TLRef i)
                        (or
                             ex2_2 C T λd0:C.λu0:T.getl i d (CHead d0 (Bind Abbr) u0) λd0:C.λu0:T.arity g d0 u0 a0
                             ex2_2 C T λd0:C.λu0:T.getl i d (CHead d0 (Bind Abst) u0) λd0:C.λu0:T.arity g d0 u0 (asucc g a0))
                      suppose H4eq T (TLRef i0) (TLRef i)
                         (H5
                            by (f_equal . . . . . H4)
                            we proved 
                               eq
                                 nat
                                 <λ:T.nat> CASE TLRef i0 OF TSort i0 | TLRef nn | THead   i0
                                 <λ:T.nat> CASE TLRef i OF TSort i0 | TLRef nn | THead   i0

                               eq
                                 nat
                                 λe:T.<λ:T.nat> CASE e OF TSort i0 | TLRef nn | THead   i0 (TLRef i0)
                                 λe:T.<λ:T.nat> CASE e OF TSort i0 | TLRef nn | THead   i0 (TLRef i)
                         end of H5
                         (H6
                            consider H5
                            we proved 
                               eq
                                 nat
                                 <λ:T.nat> CASE TLRef i0 OF TSort i0 | TLRef nn | THead   i0
                                 <λ:T.nat> CASE TLRef i OF TSort i0 | TLRef nn | THead   i0
                            that is equivalent to eq nat i0 i
                            we proceed by induction on the previous result to prove getl i c0 (CHead d (Bind Abbr) u)
                               case refl_equal : 
                                  the thesis becomes the hypothesis H1
getl i c0 (CHead d (Bind Abbr) u)
                         end of H6
                         by (ex2_2_intro . . . . . . H6 H2)
                         we proved ex2_2 C T λd0:C.λu0:T.getl i c0 (CHead d0 (Bind Abbr) u0) λd0:C.λu0:T.arity g d0 u0 a0
                         by (or_introl . . previous)
                         we proved 
                            or
                              ex2_2 C T λd0:C.λu0:T.getl i c0 (CHead d0 (Bind Abbr) u0) λd0:C.λu0:T.arity g d0 u0 a0
                              ex2_2 C T λd0:C.λu0:T.getl i c0 (CHead d0 (Bind Abst) u0) λd0:C.λu0:T.arity g d0 u0 (asucc g a0)

                         H4:eq T (TLRef i0) (TLRef i)
                           .or
                             ex2_2 C T λd0:C.λu0:T.getl i c0 (CHead d0 (Bind Abbr) u0) λd0:C.λu0:T.arity g d0 u0 a0
                             ex2_2 C T λd0:C.λu0:T.getl i c0 (CHead d0 (Bind Abst) u0) λd0:C.λu0:T.arity g d0 u0 (asucc g a0)
                case arity_abst : c0:C d:C u:T i0:nat H1:getl i0 c0 (CHead d (Bind Abst) u) a0:A H2:arity g d u (asucc g a0) 
                   the thesis becomes 
                   H4:eq T (TLRef i0) (TLRef i)
                     .or
                       ex2_2 C T λd0:C.λu0:T.getl i c0 (CHead d0 (Bind Abbr) u0) λd0:C.λu0:T.arity g d0 u0 a0
                       ex2_2 C T λd0:C.λu0:T.getl i c0 (CHead d0 (Bind Abst) u0) λd0:C.λu0:T.arity g d0 u0 (asucc g a0)
                   () by induction hypothesis we know 
                      eq T u (TLRef i)
                        (or
                             ex2_2 C T λd0:C.λu0:T.getl i d (CHead d0 (Bind Abbr) u0) λd0:C.λu0:T.arity g d0 u0 (asucc g a0)
                             ex2_2
                               C
                               T
                               λd0:C.λu0:T.getl i d (CHead d0 (Bind Abst) u0)
                               λd0:C.λu0:T.arity g d0 u0 (asucc g (asucc g a0)))
                      suppose H4eq T (TLRef i0) (TLRef i)
                         (H5
                            by (f_equal . . . . . H4)
                            we proved 
                               eq
                                 nat
                                 <λ:T.nat> CASE TLRef i0 OF TSort i0 | TLRef nn | THead   i0
                                 <λ:T.nat> CASE TLRef i OF TSort i0 | TLRef nn | THead   i0

                               eq
                                 nat
                                 λe:T.<λ:T.nat> CASE e OF TSort i0 | TLRef nn | THead   i0 (TLRef i0)
                                 λe:T.<λ:T.nat> CASE e OF TSort i0 | TLRef nn | THead   i0 (TLRef i)
                         end of H5
                         (H6
                            consider H5
                            we proved 
                               eq
                                 nat
                                 <λ:T.nat> CASE TLRef i0 OF TSort i0 | TLRef nn | THead   i0
                                 <λ:T.nat> CASE TLRef i OF TSort i0 | TLRef nn | THead   i0
                            that is equivalent to eq nat i0 i
                            we proceed by induction on the previous result to prove getl i c0 (CHead d (Bind Abst) u)
                               case refl_equal : 
                                  the thesis becomes the hypothesis H1
getl i c0 (CHead d (Bind Abst) u)
                         end of H6
                         by (ex2_2_intro . . . . . . H6 H2)
                         we proved ex2_2 C T λd0:C.λu0:T.getl i c0 (CHead d0 (Bind Abst) u0) λd0:C.λu0:T.arity g d0 u0 (asucc g a0)
                         by (or_intror . . previous)
                         we proved 
                            or
                              ex2_2 C T λd0:C.λu0:T.getl i c0 (CHead d0 (Bind Abbr) u0) λd0:C.λu0:T.arity g d0 u0 a0
                              ex2_2 C T λd0:C.λu0:T.getl i c0 (CHead d0 (Bind Abst) u0) λd0:C.λu0:T.arity g d0 u0 (asucc g a0)

                         H4:eq T (TLRef i0) (TLRef i)
                           .or
                             ex2_2 C T λd0:C.λu0:T.getl i c0 (CHead d0 (Bind Abbr) u0) λd0:C.λu0:T.arity g d0 u0 a0
                             ex2_2 C T λd0:C.λu0:T.getl i c0 (CHead d0 (Bind Abst) u0) λd0:C.λu0:T.arity g d0 u0 (asucc g a0)
                case arity_bind : b:B :not (eq B b Abst) c0:C u:T a1:A :arity g c0 u a1 t:T a2:A :arity g (CHead c0 (Bind b) u) t a2 
                   the thesis becomes 
                   H6:eq T (THead (Bind b) u t) (TLRef i)
                     .or
                       ex2_2 C T λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0) λd:C.λu0:T.arity g d u0 a2
                       ex2_2
                         C
                         T
                         λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                         λd:C.λu0:T.arity g d u0 (asucc g a2)
                   () by induction hypothesis we know 
                      eq T u (TLRef i)
                        (or
                             ex2_2 C T λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0) λd:C.λu0:T.arity g d u0 a1
                             ex2_2
                               C
                               T
                               λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                               λd:C.λu0:T.arity g d u0 (asucc g a1))
                   () by induction hypothesis we know 
                      eq T t (TLRef i)
                        (or
                             ex2_2
                               C
                               T
                               λd:C.λu0:T.getl i (CHead c0 (Bind b) u) (CHead d (Bind Abbr) u0)
                               λd:C.λu0:T.arity g d u0 a2
                             ex2_2
                               C
                               T
                               λd:C.λu0:T.getl i (CHead c0 (Bind b) u) (CHead d (Bind Abst) u0)
                               λd:C.λu0:T.arity g d u0 (asucc g a2))
                      suppose H6eq T (THead (Bind b) u t) (TLRef i)
                         (H7
                            we proceed by induction on H6 to prove 
                               <λ:T.Prop>
                                 CASE TLRef i OF
                                   TSort False
                                 | TLRef False
                                 | THead   True
                               case refl_equal : 
                                  the thesis becomes 
                                  <λ:T.Prop>
                                    CASE THead (Bind b) u t OF
                                      TSort False
                                    | TLRef False
                                    | THead   True
                                     consider I
                                     we proved True

                                        <λ:T.Prop>
                                          CASE THead (Bind b) u t OF
                                            TSort False
                                          | TLRef False
                                          | THead   True

                               <λ:T.Prop>
                                 CASE TLRef i OF
                                   TSort False
                                 | TLRef False
                                 | THead   True
                         end of H7
                         consider H7
                         we proved 
                            <λ:T.Prop>
                              CASE TLRef i OF
                                TSort False
                              | TLRef False
                              | THead   True
                         that is equivalent to False
                         we proceed by induction on the previous result to prove 
                            or
                              ex2_2 C T λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0) λd:C.λu0:T.arity g d u0 a2
                              ex2_2
                                C
                                T
                                λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                                λd:C.λu0:T.arity g d u0 (asucc g a2)
                         we proved 
                            or
                              ex2_2 C T λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0) λd:C.λu0:T.arity g d u0 a2
                              ex2_2
                                C
                                T
                                λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                                λd:C.λu0:T.arity g d u0 (asucc g a2)

                         H6:eq T (THead (Bind b) u t) (TLRef i)
                           .or
                             ex2_2 C T λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0) λd:C.λu0:T.arity g d u0 a2
                             ex2_2
                               C
                               T
                               λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                               λd:C.λu0:T.arity g d u0 (asucc g a2)
                case arity_head : c0:C u:T a1:A :arity g c0 u (asucc g a1) t:T a2:A :arity g (CHead c0 (Bind Abst) u) t a2 
                   the thesis becomes 
                   H5:eq T (THead (Bind Abst) u t) (TLRef i)
                     .or
                       ex2_2
                         C
                         T
                         λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0)
                         λd:C.λu0:T.arity g d u0 (AHead a1 a2)
                       ex2_2
                         C
                         T
                         λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                         λd:C.λu0:T.arity g d u0 (asucc g (AHead a1 a2))
                   () by induction hypothesis we know 
                      eq T u (TLRef i)
                        (or
                             ex2_2
                               C
                               T
                               λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0)
                               λd:C.λu0:T.arity g d u0 (asucc g a1)
                             ex2_2
                               C
                               T
                               λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                               λd:C.λu0:T.arity g d u0 (asucc g (asucc g a1)))
                   () by induction hypothesis we know 
                      eq T t (TLRef i)
                        (or
                             ex2_2
                               C
                               T
                               λd:C.λu0:T.getl i (CHead c0 (Bind Abst) u) (CHead d (Bind Abbr) u0)
                               λd:C.λu0:T.arity g d u0 a2
                             ex2_2
                               C
                               T
                               λd:C.λu0:T.getl i (CHead c0 (Bind Abst) u) (CHead d (Bind Abst) u0)
                               λd:C.λu0:T.arity g d u0 (asucc g a2))
                      suppose H5eq T (THead (Bind Abst) u t) (TLRef i)
                         (H6
                            we proceed by induction on H5 to prove 
                               <λ:T.Prop>
                                 CASE TLRef i OF
                                   TSort False
                                 | TLRef False
                                 | THead   True
                               case refl_equal : 
                                  the thesis becomes 
                                  <λ:T.Prop>
                                    CASE THead (Bind Abst) u t OF
                                      TSort False
                                    | TLRef False
                                    | THead   True
                                     consider I
                                     we proved True

                                        <λ:T.Prop>
                                          CASE THead (Bind Abst) u t OF
                                            TSort False
                                          | TLRef False
                                          | THead   True

                               <λ:T.Prop>
                                 CASE TLRef i OF
                                   TSort False
                                 | TLRef False
                                 | THead   True
                         end of H6
                         consider H6
                         we proved 
                            <λ:T.Prop>
                              CASE TLRef i OF
                                TSort False
                              | TLRef False
                              | THead   True
                         that is equivalent to False
                         we proceed by induction on the previous result to prove 
                            or
                              ex2_2
                                C
                                T
                                λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0)
                                λd:C.λu0:T.arity g d u0 (AHead a1 a2)
                              ex2_2
                                C
                                T
                                λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                                λd:C.λu0:T.arity g d u0 (asucc g (AHead a1 a2))
                         we proved 
                            or
                              ex2_2
                                C
                                T
                                λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0)
                                λd:C.λu0:T.arity g d u0 (AHead a1 a2)
                              ex2_2
                                C
                                T
                                λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                                λd:C.λu0:T.arity g d u0 (asucc g (AHead a1 a2))

                         H5:eq T (THead (Bind Abst) u t) (TLRef i)
                           .or
                             ex2_2
                               C
                               T
                               λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0)
                               λd:C.λu0:T.arity g d u0 (AHead a1 a2)
                             ex2_2
                               C
                               T
                               λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                               λd:C.λu0:T.arity g d u0 (asucc g (AHead a1 a2))
                case arity_appl : c0:C u:T a1:A :arity g c0 u a1 t:T a2:A :arity g c0 t (AHead a1 a2) 
                   the thesis becomes 
                   H5:eq T (THead (Flat Appl) u t) (TLRef i)
                     .or
                       ex2_2 C T λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0) λd:C.λu0:T.arity g d u0 a2
                       ex2_2
                         C
                         T
                         λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                         λd:C.λu0:T.arity g d u0 (asucc g a2)
                   () by induction hypothesis we know 
                      eq T u (TLRef i)
                        (or
                             ex2_2 C T λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0) λd:C.λu0:T.arity g d u0 a1
                             ex2_2
                               C
                               T
                               λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                               λd:C.λu0:T.arity g d u0 (asucc g a1))
                   () by induction hypothesis we know 
                      eq T t (TLRef i)
                        (or
                             ex2_2
                               C
                               T
                               λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0)
                               λd:C.λu0:T.arity g d u0 (AHead a1 a2)
                             ex2_2
                               C
                               T
                               λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                               λd:C.λu0:T.arity g d u0 (asucc g (AHead a1 a2)))
                      suppose H5eq T (THead (Flat Appl) u t) (TLRef i)
                         (H6
                            we proceed by induction on H5 to prove 
                               <λ:T.Prop>
                                 CASE TLRef i OF
                                   TSort False
                                 | TLRef False
                                 | THead   True
                               case refl_equal : 
                                  the thesis becomes 
                                  <λ:T.Prop>
                                    CASE THead (Flat Appl) u t OF
                                      TSort False
                                    | TLRef False
                                    | THead   True
                                     consider I
                                     we proved True

                                        <λ:T.Prop>
                                          CASE THead (Flat Appl) u t OF
                                            TSort False
                                          | TLRef False
                                          | THead   True

                               <λ:T.Prop>
                                 CASE TLRef i OF
                                   TSort False
                                 | TLRef False
                                 | THead   True
                         end of H6
                         consider H6
                         we proved 
                            <λ:T.Prop>
                              CASE TLRef i OF
                                TSort False
                              | TLRef False
                              | THead   True
                         that is equivalent to False
                         we proceed by induction on the previous result to prove 
                            or
                              ex2_2 C T λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0) λd:C.λu0:T.arity g d u0 a2
                              ex2_2
                                C
                                T
                                λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                                λd:C.λu0:T.arity g d u0 (asucc g a2)
                         we proved 
                            or
                              ex2_2 C T λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0) λd:C.λu0:T.arity g d u0 a2
                              ex2_2
                                C
                                T
                                λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                                λd:C.λu0:T.arity g d u0 (asucc g a2)

                         H5:eq T (THead (Flat Appl) u t) (TLRef i)
                           .or
                             ex2_2 C T λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0) λd:C.λu0:T.arity g d u0 a2
                             ex2_2
                               C
                               T
                               λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                               λd:C.λu0:T.arity g d u0 (asucc g a2)
                case arity_cast : c0:C u:T a0:A :arity g c0 u (asucc g a0) t:T :arity g c0 t a0 
                   the thesis becomes 
                   H5:eq T (THead (Flat Cast) u t) (TLRef i)
                     .or
                       ex2_2 C T λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0) λd:C.λu0:T.arity g d u0 a0
                       ex2_2
                         C
                         T
                         λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                         λd:C.λu0:T.arity g d u0 (asucc g a0)
                   () by induction hypothesis we know 
                      eq T u (TLRef i)
                        (or
                             ex2_2
                               C
                               T
                               λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0)
                               λd:C.λu0:T.arity g d u0 (asucc g a0)
                             ex2_2
                               C
                               T
                               λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                               λd:C.λu0:T.arity g d u0 (asucc g (asucc g a0)))
                   () by induction hypothesis we know 
                      eq T t (TLRef i)
                        (or
                             ex2_2 C T λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0) λd:C.λu0:T.arity g d u0 a0
                             ex2_2
                               C
                               T
                               λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                               λd:C.λu0:T.arity g d u0 (asucc g a0))
                      suppose H5eq T (THead (Flat Cast) u t) (TLRef i)
                         (H6
                            we proceed by induction on H5 to prove 
                               <λ:T.Prop>
                                 CASE TLRef i OF
                                   TSort False
                                 | TLRef False
                                 | THead   True
                               case refl_equal : 
                                  the thesis becomes 
                                  <λ:T.Prop>
                                    CASE THead (Flat Cast) u t OF
                                      TSort False
                                    | TLRef False
                                    | THead   True
                                     consider I
                                     we proved True

                                        <λ:T.Prop>
                                          CASE THead (Flat Cast) u t OF
                                            TSort False
                                          | TLRef False
                                          | THead   True

                               <λ:T.Prop>
                                 CASE TLRef i OF
                                   TSort False
                                 | TLRef False
                                 | THead   True
                         end of H6
                         consider H6
                         we proved 
                            <λ:T.Prop>
                              CASE TLRef i OF
                                TSort False
                              | TLRef False
                              | THead   True
                         that is equivalent to False
                         we proceed by induction on the previous result to prove 
                            or
                              ex2_2 C T λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0) λd:C.λu0:T.arity g d u0 a0
                              ex2_2
                                C
                                T
                                λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                                λd:C.λu0:T.arity g d u0 (asucc g a0)
                         we proved 
                            or
                              ex2_2 C T λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0) λd:C.λu0:T.arity g d u0 a0
                              ex2_2
                                C
                                T
                                λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                                λd:C.λu0:T.arity g d u0 (asucc g a0)

                         H5:eq T (THead (Flat Cast) u t) (TLRef i)
                           .or
                             ex2_2 C T λd:C.λu0:T.getl i c0 (CHead d (Bind Abbr) u0) λd:C.λu0:T.arity g d u0 a0
                             ex2_2
                               C
                               T
                               λd:C.λu0:T.getl i c0 (CHead d (Bind Abst) u0)
                               λd:C.λu0:T.arity g d u0 (asucc g a0)
                case arity_repl : c0:C t:T a1:A H1:arity g c0 t a1 a2:A H3:leq g a1 a2 
                   the thesis becomes 
                   H4:eq T t (TLRef i)
                     .or
                       ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a2
                       ex2_2
                         C
                         T
                         λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                         λd:C.λu:T.arity g d u (asucc g a2)
                   (H2) by induction hypothesis we know 
                      eq T t (TLRef i)
                        (or
                             ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a1
                             ex2_2
                               C
                               T
                               λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                               λd:C.λu:T.arity g d u (asucc g a1))
                      suppose H4eq T t (TLRef i)
                         (H5
                            by (f_equal . . . . . H4)
                            we proved eq T t (TLRef i)
eq T (λe:T.e t) (λe:T.e (TLRef i))
                         end of H5
                         (H6
                            we proceed by induction on H5 to prove 
                               eq T (TLRef i) (TLRef i)
                                 (or
                                      ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a1
                                      ex2_2
                                        C
                                        T
                                        λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                                        λd:C.λu:T.arity g d u (asucc g a1))
                               case refl_equal : 
                                  the thesis becomes the hypothesis H2

                               eq T (TLRef i) (TLRef i)
                                 (or
                                      ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a1
                                      ex2_2
                                        C
                                        T
                                        λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                                        λd:C.λu:T.arity g d u (asucc g a1))
                         end of H6
                         (H8
                            by (refl_equal . .)
                            we proved eq T (TLRef i) (TLRef i)
                            by (H6 previous)

                               or
                                 ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a1
                                 ex2_2
                                   C
                                   T
                                   λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                                   λd:C.λu:T.arity g d u (asucc g a1)
                         end of H8
                         we proceed by induction on H8 to prove 
                            or
                              ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a2
                              ex2_2
                                C
                                T
                                λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                                λd:C.λu:T.arity g d u (asucc g a2)
                            case or_introl : H9:ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a1 
                               the thesis becomes 
                               or
                                 ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a2
                                 ex2_2
                                   C
                                   T
                                   λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                                   λd:C.λu:T.arity g d u (asucc g a2)
                                  we proceed by induction on H9 to prove 
                                     or
                                       ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a2
                                       ex2_2
                                         C
                                         T
                                         λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                                         λd:C.λu:T.arity g d u (asucc g a2)
                                     case ex2_2_intro : x0:C x1:T H10:getl i c0 (CHead x0 (Bind Abbr) x1) H11:arity g x0 x1 a1 
                                        the thesis becomes 
                                        or
                                          ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a2
                                          ex2_2
                                            C
                                            T
                                            λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                                            λd:C.λu:T.arity g d u (asucc g a2)
                                           by (arity_repl . . . . H11 . H3)
                                           we proved arity g x0 x1 a2
                                           by (ex2_2_intro . . . . . . H10 previous)
                                           we proved ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a2
                                           by (or_introl . . previous)

                                              or
                                                ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a2
                                                ex2_2
                                                  C
                                                  T
                                                  λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                                                  λd:C.λu:T.arity g d u (asucc g a2)

                                     or
                                       ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a2
                                       ex2_2
                                         C
                                         T
                                         λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                                         λd:C.λu:T.arity g d u (asucc g a2)
                            case or_intror : H9:ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u) λd:C.λu:T.arity g d u (asucc g a1) 
                               the thesis becomes 
                               or
                                 ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a2
                                 ex2_2
                                   C
                                   T
                                   λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                                   λd:C.λu:T.arity g d u (asucc g a2)
                                  we proceed by induction on H9 to prove 
                                     or
                                       ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a2
                                       ex2_2
                                         C
                                         T
                                         λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                                         λd:C.λu:T.arity g d u (asucc g a2)
                                     case ex2_2_intro : x0:C x1:T H10:getl i c0 (CHead x0 (Bind Abst) x1) H11:arity g x0 x1 (asucc g a1) 
                                        the thesis becomes 
                                        or
                                          ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a2
                                          ex2_2
                                            C
                                            T
                                            λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                                            λd:C.λu:T.arity g d u (asucc g a2)
                                           by (asucc_repl . . . H3)
                                           we proved leq g (asucc g a1) (asucc g a2)
                                           by (arity_repl . . . . H11 . previous)
                                           we proved arity g x0 x1 (asucc g a2)
                                           by (ex2_2_intro . . . . . . H10 previous)
                                           we proved 
                                              ex2_2
                                                C
                                                T
                                                λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                                                λd:C.λu:T.arity g d u (asucc g a2)
                                           by (or_intror . . previous)

                                              or
                                                ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a2
                                                ex2_2
                                                  C
                                                  T
                                                  λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                                                  λd:C.λu:T.arity g d u (asucc g a2)

                                     or
                                       ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a2
                                       ex2_2
                                         C
                                         T
                                         λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                                         λd:C.λu:T.arity g d u (asucc g a2)
                         we proved 
                            or
                              ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a2
                              ex2_2
                                C
                                T
                                λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                                λd:C.λu:T.arity g d u (asucc g a2)

                         H4:eq T t (TLRef i)
                           .or
                             ex2_2 C T λd:C.λu:T.getl i c0 (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a2
                             ex2_2
                               C
                               T
                               λd:C.λu:T.getl i c0 (CHead d (Bind Abst) u)
                               λd:C.λu:T.arity g d u (asucc g a2)
             we proved 
                eq T y (TLRef i)
                  (or
                       ex2_2 C T λd:C.λu:T.getl i c (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a
                       ex2_2
                         C
                         T
                         λd:C.λu:T.getl i c (CHead d (Bind Abst) u)
                         λd:C.λu:T.arity g d u (asucc g a))
          we proved 
             y:T
               .arity g c y a
                 (eq T y (TLRef i)
                      (or
                           ex2_2 C T λd:C.λu:T.getl i c (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a
                           ex2_2
                             C
                             T
                             λd:C.λu:T.getl i c (CHead d (Bind Abst) u)
                             λd:C.λu:T.arity g d u (asucc g a)))
          by (insert_eq . . . . previous H)
          we proved 
             or
               ex2_2 C T λd:C.λu:T.getl i c (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a
               ex2_2
                 C
                 T
                 λd:C.λu:T.getl i c (CHead d (Bind Abst) u)
                 λd:C.λu:T.arity g d u (asucc g a)
       we proved 
          g:G
            .c:C
              .i:nat
                .a:A
                  .arity g c (TLRef i) a
                    (or
                         ex2_2 C T λd:C.λu:T.getl i c (CHead d (Bind Abbr) u) λd:C.λu:T.arity g d u a
                         ex2_2
                           C
                           T
                           λd:C.λu:T.getl i c (CHead d (Bind Abst) u)
                           λd:C.λu:T.arity g d u (asucc g a))