YES(?,O(n^1))

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

Proof:
 Bounds Processor:
  bound: 1
  enrichment: match
  automaton:
   final states: {3}
   transitions:
    f1(8,3) -> 9*
    f1(8,11) -> 9,3
    f1(10,9) -> 11*
    f1(8,8) -> 10*
    a1() -> 8*
    f0(3,3) -> 3*
    a0() -> 3*
  problem:
   
  Qed