proposition: Theorem lt_Acc : forall n:nat, Acc lt n.
proof: Proof. induction n. - split; intros p H; inversion H. - split; intros y H0. inversion H0. + assumption. + destruct IHn; auto. Qed.
imports: ZArith List Arith Lia Zwf Relations Inverse_Image Transitive_Closure