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