MAYBE
28.47/10.18	MAYBE
28.47/10.18	
28.47/10.18	Problem:
28.47/10.18	 a(x1) -> x1
28.47/10.18	 a(a(a(x1))) -> b(x1)
28.47/10.18	 b(c(x1)) -> a(c(c(b(x1))))
28.47/10.18	 c(x1) -> x1
28.47/10.18	
28.47/10.18	Proof:
28.47/10.18	 Open
28.47/10.19	EOF