MAYBE
0.08/0.17	MAYBE
0.08/0.17	
0.08/0.17	Problem:
0.08/0.17	 ack(0(),y) -> s(y)
0.08/0.17	 ack(s(x),0()) -> ack(x,s(0()))
0.08/0.17	 ack(s(x),s(y)) -> ack(x,ack(s(x),y))
0.08/0.17	
0.08/0.17	Proof:
0.08/0.17	 Open
0.08/0.18	EOF