MAYBE We are left with following problem, upon which TcT provides the certificate MAYBE. Strict Trs: { a__f(X1, X2, X3) -> f(X1, X2, X3) , a__f(a(), b(), X) -> a__f(X, X, mark(X)) , mark(a()) -> a() , mark(b()) -> b() , mark(f(X1, X2, X3)) -> a__f(X1, X2, mark(X3)) , mark(c()) -> a__c() , a__c() -> a() , a__c() -> b() , a__c() -> c() } Obligation: innermost runtime complexity Answer: MAYBE The input cannot be shown compatible Arrrr..