proposition: Lemma add_reduce6 : forall x y z : Z, x = (z + y)%Z -> (x - z)%Z = y.
proof: Proof. intros; omega. Qed.
imports: List DistributedReferenceCounting.machine2.invariant0 DistributedReferenceCounting.machine2.invariant1 DistributedReferenceCounting.machine2.invariant2