a b c : Nat
h₁ : a = b
h₂ : b = c
⊢ a = b
case h
a : Nat
⊢ ?w = a

case w
a : Nat
⊢ Nat
case h
a : Nat
⊢ ?w = a
case w
a : Nat
⊢ Nat

case h
a : Nat
⊢ ?w = a
case h
a : Nat
⊢ a = a