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