We are left with following problem, upon which TcT provides the certificate YES(?,O(n^1)). Strict Trs: { rec(rec(x)) -> sent(rec(x)) , rec(sent(x)) -> sent(rec(x)) , rec(no(x)) -> sent(rec(x)) , rec(bot()) -> up(sent(bot())) , rec(up(x)) -> up(rec(x)) , sent(up(x)) -> up(sent(x)) , no(up(x)) -> up(no(x)) , top(rec(up(x))) -> top(check(rec(x))) , top(sent(up(x))) -> top(check(rec(x))) , top(no(up(x))) -> top(check(rec(x))) , check(rec(x)) -> rec(check(x)) , check(sent(x)) -> sent(check(x)) , check(no(x)) -> no(x) , check(no(x)) -> no(check(x)) , check(up(x)) -> up(check(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. { rec_0(4) -> 1 , rec_0(5) -> 1 , rec_1(4) -> 8 , rec_1(5) -> 8 , sent_0(4) -> 2 , sent_0(5) -> 2 , sent_1(4) -> 10 , sent_1(5) -> 10 , sent_1(9) -> 8 , no_0(4) -> 3 , no_0(5) -> 3 , no_1(4) -> 11 , no_1(5) -> 11 , bot_0() -> 4 , bot_1() -> 9 , up_0(4) -> 5 , up_0(5) -> 5 , up_1(8) -> 1 , up_1(8) -> 8 , up_1(10) -> 2 , up_1(10) -> 10 , up_1(11) -> 3 , up_1(11) -> 11 , up_1(12) -> 7 , up_1(12) -> 12 , top_0(4) -> 6 , top_0(5) -> 6 , check_0(4) -> 7 , check_0(5) -> 7 , check_1(4) -> 12 , check_1(5) -> 12 } Hurray, we answered YES(?,O(n^1))