exact l.get_concat_length a _
α : Type u
a : α
i : Nat
l : List α
h : i < List.length (List.concat l a)
hil : ¬i < List.length l
this : i = List.length l
⊢ List.get (l ++ [a]) { val := List.length l, isLt := (_ : List.length l < List.length (l ++ [a])) } = a
no goals