apply Nat.le_refl
case cons.inr.a
α : Type u_1
inst✝ : DecidableEq α
x : α
xs : List α
ih : ∀ (as : List α), length (uniqueAux xs as) ≤ length xs + length as
as : List α
h : ¬x ∈ as
⊢ length xs + (1 + length as) ≤ length xs + (1 + length as)
no goals