MAYBE
29.50/10.19	MAYBE
29.50/10.19	
29.50/10.19	Problem:
29.50/10.19	 double(0()) -> 0()
29.50/10.19	 double(s(x)) -> s(s(double(x)))
29.50/10.19	 half(0()) -> 0()
29.50/10.19	 half(s(0())) -> 0()
29.50/10.19	 half(s(s(x))) -> s(half(x))
29.50/10.19	 -(x,0()) -> x
29.50/10.19	 -(s(x),s(y)) -> -(x,y)
29.50/10.19	 if(0(),y,z) -> y
29.50/10.19	 if(s(x),y,z) -> z
29.50/10.19	 half(double(x)) -> x
29.50/10.19	
29.50/10.19	Proof:
29.50/10.19	 Open
29.50/10.19	EOF