intro n₂ (_ : step n₁ ≃ step n₂)
ℕ : Type
inst✝² : Core ℕ
inst✝¹ : Induction ℕ
inst✝ : Addition ℕ
n₁✝ n₂✝ m n₁ : ℕ
ih : ∀ (y : ℕ), n₁ ≃ y → n₁ + m ≃ y + m
n₂ : ℕ
⊢ ∀ (m_1 : ℕ), step n₁ ≃ step m_1 → step n₁ + m ≃ step m_1 + m
ℕ : Type
inst✝² : Core ℕ
inst✝¹ : Induction ℕ
inst✝ : Addition ℕ
n₁✝ n₂✝¹ m n₁ : ℕ
ih : ∀ (y : ℕ), n₁ ≃ y → n₁ + m ≃ y + m
n₂✝ n₂ : ℕ
x✝ : step n₁ ≃ step n₂
⊢ step n₁ + m ≃ step n₂ + m