MAYBE We are left with following problem, upon which TcT provides the certificate MAYBE. Strict Trs: { -(x, 0()) -> x , -(s(x), s(y)) -> -(x, y) , +(0(), y) -> y , +(s(x), y) -> s(+(x, y)) , *(x, 0()) -> 0() , *(x, s(y)) -> +(x, *(x, y)) , f(s(x), y) -> f(-(*(s(x), s(y)), s(*(s(x), y))), *(y, y)) } Obligation: innermost runtime complexity Answer: MAYBE The input cannot be shown compatible Arrrr..