YES
O(n)
TRS:
 {f(a(), f(a(), x)) -> f(a(), f(f(a(), a()), f(a(), x)))}
 DUP: We consider a non-duplicating system.
  Trs:
   {f(a(), f(a(), x)) -> f(a(), f(f(a(), a()), f(a(), x)))}
  BOUND:
   Automaton:
    {
           a_2() -> 11,
           a_1() -> 3,
           a_0() -> 2,
     f_2(12, 13) -> 14,
     f_2(11, 14) -> 5,
     f_2(11, 11) -> 12,
      f_2(11, 6) -> 13,
       f_1(4, 5) -> 6,
       f_1(3, 6) -> 5 | 2,
       f_1(3, 3) -> 4,
       f_1(3, 2) -> 5,
       f_0(2, 2) -> 2
    }
   Strict:
    {}
   Qed