MAYBE
136.56/55.47	MAYBE
136.56/55.47	
136.56/55.47	Problem:
136.56/55.47	 a(a(x1)) -> b(b(b(x1)))
136.56/55.47	 a(x1) -> d(c(d(x1)))
136.56/55.47	 b(b(x1)) -> c(c(c(x1)))
136.56/55.47	 c(c(x1)) -> d(d(d(x1)))
136.56/55.47	 c(d(d(x1))) -> a(x1)
136.56/55.47	
136.56/55.47	Proof:
136.56/55.47	 Open
136.56/55.47	EOF