YES(?,POLY) We are left with following problem, upon which TcT provides the certificate YES(?,POLY). Strict Trs: { and(tt(), X) -> activate(X) , activate(X) -> X , plus(N, 0()) -> N , plus(N, s(M)) -> s(plus(N, M)) } Obligation: innermost runtime complexity Answer: YES(?,POLY) The input was oriented with the instance of 'Polynomial Path Order' as induced by the safe mapping safe(and) = {}, safe(tt) = {}, safe(activate) = {}, safe(plus) = {1}, safe(0) = {}, safe(s) = {1} and precedence and > plus, activate > plus, and ~ activate . Following symbols are considered recursive: {and, activate, plus} The recursion depth is 2. For your convenience, here are the satisfied ordering constraints: and(tt(), X;) > activate(X;) activate(X;) > X plus(0(); N) > N plus(s(; M); N) > s(; plus(M; N)) Hurray, we answered YES(?,POLY)