intro n (ih : n + m ≃ m + n)
ℕ : Type
inst✝² : Core ℕ
inst✝¹ : Induction ℕ
inst✝ : Addition ℕ
n m : ℕ
⊢ ∀ (m_1 : ℕ), m_1 + m ≃ m + m_1 → step m_1 + m ≃ m + step m_1
ℕ : Type
inst✝² : Core ℕ
inst✝¹ : Induction ℕ
inst✝ : Addition ℕ
n✝ m n : ℕ
ih : n + m ≃ m + n
⊢ step n + m ≃ m + step n