proposition: Theorem spec_to_Z_pos: forall n, (0 <= BigZ.to_Z n)%Z -> BigN.to_Z (BigZ.to_N n) = BigZ.to_Z n.
proof: Proof. intros n; case n; simpl; intros p; generalize (BigN.spec_pos p); case (BigN.to_Z p); auto. intros p1 _ H1; case H1; auto. intros p1 H1; case H1; auto. Qed.
imports: BigN ZProperties ZDivFloor ZSig ZSigZAxioms ZMake Ring Lia