MAYBE We are left with following problem, upon which TcT provides the certificate MAYBE. Strict Trs: { a__2nd(X) -> 2nd(X) , a__2nd(cons(X, cons(Y, Z))) -> mark(Y) , mark(cons(X1, X2)) -> cons(mark(X1), X2) , mark(from(X)) -> a__from(mark(X)) , mark(s(X)) -> s(mark(X)) , mark(2nd(X)) -> a__2nd(mark(X)) , a__from(X) -> cons(mark(X), from(s(X))) , a__from(X) -> from(X) } Obligation: innermost runtime complexity Answer: MAYBE The input cannot be shown compatible Arrrr..