proposition: Lemma Forall2_drop : forall P n r s, Forall2 P r s -> Forall2 P (drop n r) (drop n s).
proof: Proof. Proof using. intros P n. induction n; introv H; inverts H; rew_listx~. Qed.
imports: Coq.Classes.Morphisms TLC(LibTactics LibLogic LibReflect LibOperation LibProd LibOption LibNat LibInt LibWf LibMonoid LibRelation)