MAYBE We are left with following problem, upon which TcT provides the certificate MAYBE. Strict Trs: { incr(X) -> n__incr(X) , incr(nil()) -> nil() , incr(cons(X, L)) -> cons(s(X), n__incr(activate(L))) , activate(X) -> X , activate(n__incr(X)) -> incr(activate(X)) , activate(n__adx(X)) -> adx(activate(X)) , activate(n__zeros()) -> zeros() , adx(X) -> n__adx(X) , adx(nil()) -> nil() , adx(cons(X, L)) -> incr(cons(X, n__adx(activate(L)))) , nats() -> adx(zeros()) , zeros() -> cons(0(), n__zeros()) , zeros() -> n__zeros() , head(cons(X, L)) -> X , tail(cons(X, L)) -> activate(L) } Obligation: innermost runtime complexity Answer: MAYBE The input cannot be shown compatible Arrrr..