have : n < k := trans_eqv_lt_lt ‹n ≃ m› ‹m < k›
ℕ : Type
inst✝³ : Core ℕ
inst✝² : Induction ℕ
inst✝¹ : Addition ℕ
inst✝ : Sign ℕ
order_inst : Order ℕ
n m k : ℕ
x✝¹ : n ≤ m
x✝ : m < k
this : n < m ∨ n ≃ m
h✝ : n ≃ m
⊢ n < k
ℕ : Type
inst✝³ : Core ℕ
inst✝² : Induction ℕ
inst✝¹ : Addition ℕ
inst✝ : Sign ℕ
order_inst : Order ℕ
n m k : ℕ
x✝¹ : n ≤ m
x✝ : m < k
this✝ : n < m ∨ n ≃ m
h✝ : n ≃ m
this : n < k
⊢ n < k