MAYBE We are left with following problem, upon which TcT provides the certificate MAYBE. Strict Trs: { a__from(X) -> cons(mark(X), from(s(X))) , a__from(X) -> from(X) , mark(cons(X1, X2)) -> cons(mark(X1), X2) , mark(from(X)) -> a__from(mark(X)) , mark(s(X)) -> s(mark(X)) , mark(0()) -> 0() , mark(after(X1, X2)) -> a__after(mark(X1), mark(X2)) , a__after(X1, X2) -> after(X1, X2) , a__after(s(N), cons(X, XS)) -> a__after(mark(N), mark(XS)) , a__after(0(), XS) -> mark(XS) } Obligation: innermost runtime complexity Answer: MAYBE The input cannot be shown compatible Arrrr..