YES(?,O(n^1))

Problem:
 a(b(a(x1))) -> b(b(a(x1)))
 b(b(b(x1))) -> b(a(x1))
 b(b(x1)) -> a(a(a(x1)))

Proof:
 Bounds Processor:
  bound: 0
  enrichment: match
  automaton:
   final states: {3,2}
   transitions:
    a0(1) -> 2*
    b0(1) -> 3*
    f40() -> 1*
  problem:
   
  Qed