proposition: Lemma Exists_app_inv : forall P l1 l2, Exists P (l1++l2) -> Exists P l1 \/ Exists P l2.
proof: Proof. Proof using. introv H. rewrite* Exists_app_eq in H. Qed.
imports: Coq.Classes.Morphisms TLC(LibTactics LibLogic LibReflect LibOperation LibProd LibOption LibNat LibInt LibWf LibMonoid LibRelation)