We are left with following problem, upon which TcT provides the
certificate YES(?,O(n^1)).

Strict Trs:
  { f(c(X, s(Y))) -> f(c(s(X), Y))
  , g(c(s(X), Y)) -> f(c(X, s(Y))) }
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_1(5) -> 1
, f_1(7) -> 4
, f_2(8) -> 4
, c_0(2, 2) -> 2
, c_0(2, 3) -> 2
, c_0(3, 2) -> 2
, c_0(3, 3) -> 2
, c_1(2, 6) -> 7
, c_1(3, 6) -> 7
, c_1(6, 2) -> 5
, c_1(6, 3) -> 5
, c_1(10, 2) -> 7
, c_1(10, 3) -> 7
, c_2(9, 2) -> 8
, c_2(9, 3) -> 8
, c_2(9, 6) -> 8
, s_0(2) -> 3
, s_0(3) -> 3
, s_1(2) -> 6
, s_1(3) -> 6
, s_1(6) -> 6
, s_1(9) -> 10
, s_1(10) -> 10
, s_2(2) -> 9
, s_2(3) -> 9
, s_2(9) -> 9
, g_0(2) -> 4
, g_0(3) -> 4 }

Hurray, we answered YES(?,O(n^1))