MAYBE
137.79/55.38	MAYBE
137.79/55.38	
137.79/55.38	Problem:
137.79/55.38	 f(0(x1)) -> s(0(x1))
137.79/55.38	 d(0(x1)) -> 0(x1)
137.79/55.38	 d(s(x1)) -> s(s(d(x1)))
137.79/55.38	 f(s(x1)) -> d(f(x1))
137.79/55.38	
137.79/55.38	Proof:
137.79/55.38	 Open
137.79/55.38	EOF