YES(?,O(n^1))

Problem:
 f(a(),f(a(),x)) -> f(a(),f(f(a(),x),f(a(),a())))

Proof:
 Bounds Processor:
  bound: 2
  enrichment: match
  automaton:
   final states: {2,1}
   transitions:
    f1(4,2) -> 6*
    f1(4,4) -> 5*
    f1(4,1) -> 6*
    f1(4,7) -> 6,1
    f1(6,5) -> 7*
    f1(1,5) -> 7*
    a1() -> 4*
    f2(18,17) -> 19*
    f2(16,16) -> 17*
    f2(16,7) -> 18*
    f2(16,19) -> 6*
    f0(1,2) -> 1*
    f0(2,1) -> 1*
    f0(1,1) -> 1*
    f0(2,2) -> 1*
    a2() -> 16*
    a0() -> 2*
  problem:
   
  Qed