proposition: Lemma add_reduce4 : forall x y z a : Z, (x + y)%Z = (z + a)%Z -> (x - a)%Z = (z - y)%Z.
proof: Proof. intros; omega. Qed.
imports: List DistributedReferenceCounting.machine2.invariant0 DistributedReferenceCounting.machine2.invariant1 DistributedReferenceCounting.machine2.invariant2