diff --git a/DeBruijnSSA/BinSyntax/Rewrite/Region/Compose/Elgot.lean b/DeBruijnSSA/BinSyntax/Rewrite/Region/Compose/Elgot.lean
index dfe3992..aa05ce0 100644
--- a/DeBruijnSSA/BinSyntax/Rewrite/Region/Compose/Elgot.lean
+++ b/DeBruijnSSA/BinSyntax/Rewrite/Region/Compose/Elgot.lean
@@ -33,6 +33,11 @@ theorem Eqv.left_exit_eq_coprod {A B : Ty α} {Γ : Ctx α ε} {L : LCtx α}
     coprod (br 1 (var 0 (by simp)) ⟨by simp, le_refl _⟩) (ret (var 0 (by simp)))
   := rfl
 
+def Eqv.left_exit_eq_coprod' {A B : Ty α} {Γ : Ctx α ε} {L : LCtx α}
+  : left_exit (φ := φ) (A := A) (B := B) (Γ := Γ) (L := L)
+  = coprod (br 1 (var 0 (by simp)) ⟨by simp, le_refl _⟩) nil
+  := rfl
+
 theorem Eqv.lwk1_sum_seq_left_exit {A B A' B' : Ty α} {Γ : Ctx α ε} {L : LCtx α}
   {f : Eqv φ (⟨A, ⊥⟩::Γ) (A'::L)} {g : Eqv φ (⟨B, ⊥⟩::Γ) (B'::L)}
   : (sum f g).lwk1 ;; left_exit
diff --git a/DeBruijnSSA/BinSyntax/Rewrite/Region/Structural/Elgot.lean b/DeBruijnSSA/BinSyntax/Rewrite/Region/Structural/Elgot.lean
index 792fad4..60bba69 100644
--- a/DeBruijnSSA/BinSyntax/Rewrite/Region/Structural/Elgot.lean
+++ b/DeBruijnSSA/BinSyntax/Rewrite/Region/Structural/Elgot.lean
@@ -33,13 +33,11 @@ theorem Eqv.coprod_left_letc_binary {Γ : Ctx α ε}
   = letc A (coprod (l.lwk1 ;; br 1 (Term.Eqv.var 0 Ctx.Var.shead) (by simp)) β) G.vwk1 := by
   sorry
 
-theorem Eqv.letc_vwk1_den {Γ : Ctx α ε}
-  {A B : Ty α} {β : Eqv φ ((X, ⊥)::Γ) [A, B]} {G : Eqv φ ((A, ⊥)::Γ) [A, B]}
-  : letc A β G.vwk1 = (β.packed_out ;; sum (coprod zero nil) nil) ;;
-                    coprod nil (fixpoint (G.packed_out ;; coprod (coprod zero inj_l) inj_r)) := by
-  rw [fixpoint_def_vwk1, coprod_left_letc_binary, nil_lwk1, nil_seq, seq_letc_vwk1]
-  congr
-  · rw [
+theorem Eqv.packed_out_sum_coprod {β : Eqv φ ((X, ⊥)::Γ) [A, B]}
+  :  (β.packed_out ;; (zero.coprod nil).sum nil).lwk1
+      ;; (br 1 (Term.Eqv.var 0 Ctx.Var.shead) (by simp)).coprod nil = β
+  := by
+    rw [
       lwk1_seq, lwk1_packed_out, lwk1_sum, lwk1_coprod, nil_lwk1, nil_lwk1, seq, seq, packed_out,
       lsubst_lsubst, lsubst_lsubst, lsubst_id'
     ]
@@ -65,7 +63,7 @@ theorem Eqv.letc_vwk1_den {Γ : Ctx α ε}
         Term.Eqv.inj_n, Fin.cases, Fin.induction, Fin.induction.go, List.length_nil, eq_mpr_eq_cast,
         cast_eq, lsubst_br, Subst.Eqv.get_vlift, get_alpha0, lsubst_case, vwk_id_eq, vsubst_case,
         Term.Eqv.var0_subst0, Term.Eqv.wk_res_self, nil_vwk2, inj_l]
-      simp [case_inl, let1_beta]
+      simp only [case_inl, let1_beta]
       conv =>
         lhs; rhs; rhs; rhs; rhs;
         rw [
@@ -84,4 +82,18 @@ theorem Eqv.letc_vwk1_den {Γ : Ctx α ε}
         Term.Eqv.seq, Term.Eqv.inj_l, Term.Eqv.nil, <-Term.Eqv.inl_let1, case_inl, let1_beta,
         Subst.Eqv.get_id, Term.Eqv.let1_beta_pure, Nat.liftnWk, Term.Eqv.case_inr
       ]
-  · sorry
+
+
+theorem Eqv.packed_out_sum_left_exit {β : Eqv φ ((X, ⊥)::Γ) [A, B]}
+  : (β.packed_out ;; (zero.coprod nil).sum nil).lwk1 ;; left_exit = β
+  := packed_out_sum_coprod
+
+theorem Eqv.letc_vwk1_den {Γ : Ctx α ε}
+  {A B : Ty α} {β : Eqv φ ((X, ⊥)::Γ) [A, B]} {G : Eqv φ ((A, ⊥)::Γ) [A, B]}
+  : letc A β G.vwk1 = (β.packed_out ;; sum (coprod zero nil) nil) ;;
+                    coprod nil (fixpoint (G.packed_out ;; coprod (coprod zero inj_l) inj_r)) := by
+  rw [fixpoint_def_vwk1, coprod_left_letc_binary, nil_lwk1, nil_seq, seq_letc_vwk1]
+  congr
+  · rw [packed_out_sum_coprod]
+  · convert packed_out_sum_left_exit.symm
+    simp [sum, coprod_seq, zero_seq]