YES(?,O(n^1)) We are left with following problem, upon which TcT provides the certificate YES(?,O(n^1)). Strict Trs: { f(0()) -> cons(0()) , f(s(0())) -> f(p(s(0()))) , p(s(X)) -> X } 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. { f_0(2) -> 1 , f_0(3) -> 1 , f_0(4) -> 1 , f_1(7) -> 1 , 0_0() -> 2 , 0_0() -> 5 , 0_1() -> 6 , 0_1() -> 7 , 0_2() -> 9 , cons_0(2) -> 3 , cons_0(2) -> 5 , cons_0(3) -> 3 , cons_0(3) -> 5 , cons_0(4) -> 3 , cons_0(4) -> 5 , cons_1(6) -> 1 , cons_2(9) -> 1 , s_0(2) -> 4 , s_0(2) -> 5 , s_0(3) -> 4 , s_0(3) -> 5 , s_0(4) -> 4 , s_0(4) -> 5 , s_1(6) -> 8 , p_0(2) -> 5 , p_0(3) -> 5 , p_0(4) -> 5 , p_1(8) -> 7 , 2 -> 5 , 3 -> 5 , 4 -> 5 , 6 -> 7 } Hurray, we answered YES(?,O(n^1))