intros dl i j iej
α : Type u_1
inst✝ : BEq α
x y : α
xs : List α
⊢ DifferentList (x :: y :: xs) → DifferentList (y :: x :: xs)
α : Type u_1
inst✝ : BEq α
x y : α
xs : List α
dl : DifferentList (x :: y :: xs)
i j : Fin (List.length (y :: x :: xs))
iej : List.get (y :: x :: xs) i = List.get (y :: x :: xs) j
⊢ i = j