We are left with following problem, upon which TcT provides the certificate YES(?,O(n^1)). Strict Trs: { h(x, c(y, z)) -> h(c(s(y), x), z) , h(c(s(x), c(s(0()), y)), z) -> h(y, c(s(0()), c(x, z))) } Obligation: innermost runtime complexity Answer: YES(?,O(n^1)) The problem is match-bounded by 2. The enriched problem is compatible with the following automaton. { h_0(2, 2) -> 1 , h_1(2, 5) -> 1 , h_1(3, 2) -> 1 , h_1(3, 5) -> 1 , h_1(9, 5) -> 1 , h_1(11, 5) -> 1 , h_2(9, 5) -> 1 , h_2(9, 7) -> 1 , h_2(11, 2) -> 1 , h_2(11, 5) -> 1 , c_0(2, 2) -> 2 , c_1(2, 2) -> 7 , c_1(2, 5) -> 7 , c_1(4, 2) -> 3 , c_1(4, 3) -> 3 , c_1(4, 11) -> 3 , c_1(6, 5) -> 5 , c_1(6, 7) -> 5 , c_2(10, 2) -> 9 , c_2(10, 3) -> 9 , c_2(10, 9) -> 9 , c_2(10, 11) -> 9 , c_2(12, 9) -> 11 , s_0(2) -> 2 , s_1(2) -> 4 , s_1(8) -> 6 , s_2(2) -> 12 , s_2(6) -> 10 , 0_0() -> 2 , 0_1() -> 8 } Hurray, we answered YES(?,O(n^1))