YES(?,O(n^1))

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

Proof:
 Bounds Processor:
  bound: 0
  enrichment: match
  automaton:
   final states: {2}
   transitions:
    f0(1,1) -> 2*
    a0() -> 1*
  problem:
   
  Qed