proposition: Lemma Nth_app_r : forall n x l1 l2, Nth n l2 x -> Nth (n + length l1)%nat (l1 ++ l2) x.
proof: Proof. Proof using. intros. gen n. induction l1; introv H; rew_list. { applys_eq~ H. } { applys_eq* Nth_succ. } Qed.
imports: Coq.Classes.Morphisms TLC(LibTactics LibLogic LibReflect LibOperation LibProd LibOption LibNat LibInt LibWf LibMonoid LibRelation)