intros p L H'.
apply Cb_compo with (L1 := Red L); auto.
intros q H'0.
apply Red_cb; auto.
Qed.

Theorem divp_id :
forall p : poly A0 eqA ltM,
~ zerop A A0 eqA n ltM p -> divp A A0 eqA multA divA n ltM p p.