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