proposition: Lemma encode_length n l : (length l <= n)%nat -> length (encode l n) = length l.
proof: Proof. revert l; elim n; simpl; auto; clear n. intros l; case l; auto. now intros p1 l1 H; inversion H. intros n Hrec l; case l; simpl; auto. intros p1 l1 H; rewrite Hrec; auto; rewrite encode_aux_length; auto with arith. Qed.
imports: PrimInt63 Cyclic63 List BasicRubik