MAYBE
218.94/56.54	MAYBE
218.94/56.54	
218.94/56.54	Problem:
218.94/56.54	 f(f(x1)) -> b(b(b(x1)))
218.94/56.54	 a(f(x1)) -> f(a(a(x1)))
218.94/56.54	 b(b(x1)) -> c(c(a(c(x1))))
218.94/56.54	 d(b(x1)) -> d(a(b(x1)))
218.94/56.54	 c(c(x1)) -> d(d(d(x1)))
218.94/56.54	 b(d(x1)) -> d(b(x1))
218.94/56.54	 c(d(d(x1))) -> f(x1)
218.94/56.54	
218.94/56.54	Proof:
218.94/56.54	 Open
218.94/56.57	EOF