MAYBE We are left with following problem, upon which TcT provides the certificate MAYBE. Strict Trs: { from(X) -> cons(X, from(s(X))) , length(cons(X, Y)) -> s(length1(Y)) , length(nil()) -> 0() , length1(X) -> length(X) } Obligation: innermost runtime complexity Answer: MAYBE The input cannot be shown compatible Arrrr..