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