(* Leo: OUT-OF-SCOPE *)

Example trans_eq_exercise : forall (n m o p : nat),
     m = (minustwo o) ->
     (n + p) = m ->
     (n + p) = (minustwo o).

Theorem nth_error_after_last: forall (X : Type) (l : list X) (n : nat), length l = n -> nth_error l n = None.