YES(?,O(n^1)) We are left with following problem, upon which TcT provides the certificate YES(?,O(n^1)). Strict Trs: { active(c()) -> mark(f(g(c()))) , active(f(g(X))) -> mark(g(X)) , f(ok(X)) -> ok(f(X)) , g(ok(X)) -> ok(g(X)) , proper(c()) -> ok(c()) , proper(f(X)) -> f(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 6. The enriched problem is compatible with the following automaton. { active_0(2) -> 1 , active_1(2) -> 7 , active_2(5) -> 8 , active_3(19) -> 14 , active_4(22) -> 23 , active_5(20) -> 26 , active_6(29) -> 30 , c_0() -> 2 , c_1() -> 5 , c_2() -> 11 , c_3() -> 18 , c_4() -> 28 , mark_0(2) -> 2 , mark_1(3) -> 1 , mark_1(3) -> 7 , mark_2(9) -> 8 , mark_4(21) -> 14 , mark_5(24) -> 23 , f_0(2) -> 1 , f_1(2) -> 6 , f_1(4) -> 3 , f_2(10) -> 9 , f_2(12) -> 8 , f_3(15) -> 14 , f_3(17) -> 19 , f_4(20) -> 22 , g_0(2) -> 1 , g_1(2) -> 6 , g_1(5) -> 4 , g_2(11) -> 10 , g_2(13) -> 12 , g_3(11) -> 17 , g_3(16) -> 15 , g_4(11) -> 21 , g_4(18) -> 20 , g_5(18) -> 24 , g_5(25) -> 23 , g_5(28) -> 29 , g_6(27) -> 26 , proper_0(2) -> 1 , proper_1(2) -> 7 , proper_2(3) -> 8 , proper_2(4) -> 12 , proper_2(5) -> 13 , proper_3(9) -> 14 , proper_3(10) -> 15 , proper_3(11) -> 16 , proper_4(21) -> 23 , proper_5(11) -> 25 , proper_5(24) -> 26 , proper_6(18) -> 27 , ok_0(2) -> 2 , ok_1(5) -> 1 , ok_1(5) -> 7 , ok_1(6) -> 1 , ok_1(6) -> 6 , ok_2(11) -> 13 , ok_3(17) -> 12 , ok_3(18) -> 16 , ok_3(18) -> 25 , ok_3(19) -> 8 , ok_4(20) -> 15 , ok_4(20) -> 23 , ok_4(22) -> 14 , ok_4(28) -> 27 , ok_5(29) -> 26 , top_0(2) -> 1 , top_1(7) -> 1 , top_2(8) -> 1 , top_3(14) -> 1 , top_4(23) -> 1 , top_5(26) -> 1 , top_6(30) -> 1 } Hurray, we answered YES(?,O(n^1))