YES(?,O(n^1)) We are left with following problem, upon which TcT provides the certificate YES(?,O(n^1)). Strict Trs: { active(f(X)) -> f(active(X)) , active(f(f(a()))) -> mark(c(f(g(f(a()))))) , active(g(X)) -> g(active(X)) , f(mark(X)) -> mark(f(X)) , f(ok(X)) -> ok(f(X)) , c(ok(X)) -> ok(c(X)) , g(mark(X)) -> mark(g(X)) , g(ok(X)) -> ok(g(X)) , proper(f(X)) -> f(proper(X)) , proper(a()) -> ok(a()) , proper(c(X)) -> c(proper(X)) , proper(g(X)) -> g(proper(X)) , top(mark(X)) -> top(proper(X)) , top(ok(X)) -> top(active(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. { active_0(3) -> 1 , active_0(4) -> 1 , active_0(8) -> 1 , active_1(3) -> 14 , active_1(4) -> 14 , active_1(8) -> 14 , active_2(13) -> 15 , f_0(3) -> 2 , f_0(4) -> 2 , f_0(8) -> 2 , f_1(3) -> 10 , f_1(4) -> 10 , f_1(8) -> 10 , a_0() -> 3 , a_1() -> 13 , mark_0(3) -> 4 , mark_0(4) -> 4 , mark_0(8) -> 4 , mark_1(10) -> 2 , mark_1(10) -> 10 , mark_1(12) -> 6 , mark_1(12) -> 12 , c_0(3) -> 5 , c_0(4) -> 5 , c_0(8) -> 5 , c_1(3) -> 11 , c_1(4) -> 11 , c_1(8) -> 11 , g_0(3) -> 6 , g_0(4) -> 6 , g_0(8) -> 6 , g_1(3) -> 12 , g_1(4) -> 12 , g_1(8) -> 12 , proper_0(3) -> 7 , proper_0(4) -> 7 , proper_0(8) -> 7 , proper_1(3) -> 14 , proper_1(4) -> 14 , proper_1(8) -> 14 , ok_0(3) -> 8 , ok_0(4) -> 8 , ok_0(8) -> 8 , ok_1(10) -> 2 , ok_1(10) -> 10 , ok_1(11) -> 5 , ok_1(11) -> 11 , ok_1(12) -> 6 , ok_1(12) -> 12 , ok_1(13) -> 7 , ok_1(13) -> 14 , top_0(3) -> 9 , top_0(4) -> 9 , top_0(8) -> 9 , top_1(14) -> 9 , top_2(15) -> 9 } Hurray, we answered YES(?,O(n^1))