209.90/50.57	MAYBE
209.90/50.57	
209.90/50.57	Problem:
209.90/50.57	 b(b(b(b(x1)))) -> a(a(b(b(x1))))
209.90/50.57	 a(b(a(a(x1)))) -> b(a(a(b(x1))))
209.90/50.57	
209.90/50.57	Proof:
209.90/50.57	 Open
209.90/50.58	EOF