YES(?,O(n^2)) We are left with following problem, upon which TcT provides the certificate YES(?,O(n^2)). Strict Trs: { times(x, plus(y, s(z))) -> plus(times(x, plus(y, times(s(z), 0()))), times(x, s(z))) , times(x, s(y)) -> plus(times(x, y), x) , times(x, 0()) -> 0() , plus(x, s(y)) -> s(plus(x, y)) , plus(x, 0()) -> x } Obligation: innermost runtime complexity Answer: YES(?,O(n^2)) Arguments of following rules are not normal-forms: { times(x, plus(y, s(z))) -> plus(times(x, plus(y, times(s(z), 0()))), times(x, s(z))) } All above mentioned rules can be savely removed. We are left with following problem, upon which TcT provides the certificate YES(?,O(n^2)). Strict Trs: { times(x, s(y)) -> plus(times(x, y), x) , times(x, 0()) -> 0() , plus(x, s(y)) -> s(plus(x, y)) , plus(x, 0()) -> 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(times) = {}, safe(plus) = {1}, safe(s) = {1}, safe(0) = {} and precedence times > plus . Following symbols are considered recursive: {times, plus} The recursion depth is 2. For your convenience, here are the satisfied ordering constraints: times(x, s(; y);) > plus(x; times(x, y;)) times(x, 0();) > 0() plus(s(; y); x) > s(; plus(y; x)) plus(0(); x) > x Hurray, we answered YES(?,O(n^2))