exact zero_add
case a.left
ℕ : Type
inst✝³ : Core ℕ
inst✝² : Induction ℕ
inst✝¹ : Addition ℕ
inst✝ : Sign ℕ
order_inst : Order ℕ
n m✝ : ℕ
motive✝ : ℕ → Prop := fun n => AA.OneOfThree (n < m✝) (n ≃ m✝) (n > m✝)
motive : ℕ → Prop := fun m => AA.OneOfThree (0 < m) (0 ≃ m) (0 > m)
m : ℕ
⊢ 0 + step m ≃ step m
no goals