simp
case cons.inl.a.h
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 + length as ≤ length xs + length as
no goals