YES(?,O(n^1)) We are left with following problem, upon which TcT provides the certificate YES(?,O(n^1)). Strict Trs: { g(c(x, s(y))) -> g(c(s(x), y)) , f(x) -> x , f(c(s(x), y)) -> f(c(x, s(y))) , f(f(x)) -> f(d(f(x))) } Obligation: runtime complexity Answer: YES(?,O(n^1)) The problem is match-bounded by 1. The enriched problem is compatible with the following automaton. { g_0(2) -> 1 , g_1(3) -> 1 , c_0(2, 2) -> 1 , c_0(2, 2) -> 2 , c_1(2, 4) -> 1 , c_1(2, 4) -> 5 , c_1(4, 2) -> 3 , s_0(2) -> 1 , s_0(2) -> 2 , s_1(2) -> 4 , s_1(4) -> 4 , f_0(2) -> 1 , f_1(5) -> 1 , d_0(2) -> 1 , d_0(2) -> 2 , 2 -> 1 , 5 -> 1 } Hurray, we answered YES(?,O(n^1))