MAYBE
220.78/55.83	MAYBE
220.78/55.83	
220.78/55.83	Problem:
220.78/55.83	 a(a(d(d(x1)))) -> d(d(b(b(x1))))
220.78/55.83	 a(a(x1)) -> b(b(b(b(b(b(x1))))))
220.78/55.83	 b(b(d(d(b(b(x1)))))) -> a(a(c(c(x1))))
220.78/55.83	 c(c(x1)) -> d(d(x1))
220.78/55.83	
220.78/55.83	Proof:
220.78/55.83	 Open
220.78/55.84	EOF