intros
α : Type u_1
inst✝ : BEq α
i : Fin (List.length [])
⊢ ∀ (j : Fin (List.length [])), List.get [] i = List.get [] j → i = j
α : Type u_1
inst✝ : BEq α
i j✝ : Fin (List.length [])
a✝ : List.get [] i = List.get [] j✝
⊢ i = j✝