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