YES(?,O(n^1))

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

Proof:
 Bounds Processor:
  bound: 1
  enrichment: match
  automaton:
   final states: {3,2}
   transitions:
    s1(8) -> 9*
    a1(7) -> 8*
    a0(1) -> 2*
    s0(1) -> 1*
    b0(1) -> 3*
    1 -> 7*
    9 -> 8,2
  problem:
   
  Qed