MAYBE
0.08/0.18	MAYBE
0.08/0.18	
0.08/0.18	Problem:
0.08/0.18	 a__f(b(),X,c()) -> a__f(X,a__c(),X)
0.08/0.18	 a__c() -> b()
0.08/0.18	 mark(f(X1,X2,X3)) -> a__f(X1,mark(X2),X3)
0.08/0.18	 mark(c()) -> a__c()
0.08/0.18	 mark(b()) -> b()
0.08/0.18	 a__f(X1,X2,X3) -> f(X1,X2,X3)
0.08/0.18	 a__c() -> c()
0.08/0.18	
0.08/0.18	Proof:
0.08/0.18	 Open
0.08/0.18	EOF