intros.
inversion_clear H.
exists x.
inversion_clear H0; auto.
Qed.

(* Specifications: *)
Lemma has_n_elements_then_has_at_most_n_elements :
forall (A : Setoid) (n : Nat),
has_n_elements n A -> forall m : Nat, n <= m -> has_at_most_n_elements m A.