proposition: Lemma permut_tactic_simpl_eq : forall A (l1 l2 l3 l4:multiset A), (l1 \u l3) = l4 -> (l1 \u (l2 \u l3)) = (l2 \u l4).
proof: Proof. Proof using. intros. subst. apply permut_get_2. Qed.
imports: TLC(LibTactics LibLogic LibReflect LibRelation LibList LibInt LibNat LibOperation LibEpsilon LibSet LibMonoid)