intros p; elim p; simpl in |- *; auto.
intros p0 H; rewrite Zpos_xI.
apply Zlt_le_trans with (2 * (n * Zpower_nat n (pos_length p0)))%Z;
auto with zarith.
intros p0 H; rewrite Zpos_xO.
apply Zlt_le_trans with (2 * (n * Zpower_nat n (pos_length p0)))%Z;
auto with zarith.
auto with zarith.
Qed.
(* digit is correct (second part) *)

(* Specifications: *)
Theorem digitMore : forall q : Z, (Zabs q < Zpower_nat n (digit q))%Z.
intros q; case q.