proposition: Lemma lmax_perm l1 l2 : perm l1 l2 -> lmax l1 = lmax l2.
proof: Proof. intro H; elim H; clear l1 l2 H; simpl; auto. now intros a b l; repeat rewrite Nat.max_assoc; rewrite (Nat.max_comm (c2N a)); auto. intros l1 l2 l3 _ H1 _ H2; rewrite H1; auto. Qed.
imports: PrimInt63 Cyclic63 List BasicRubik Max