YES(?,O(n^1))

Problem:
 f(a()) -> f(b())
 g(b()) -> g(a())
 f(x) -> g(x)

Proof:
 Bounds Processor:
  bound: 2
  enrichment: match
  automaton:
   final states: {5}
   transitions:
    g1(10) -> 11*
    g1(16) -> 17*
    a1() -> 10*
    f1(8) -> 9*
    b1() -> 8*
    g2(22) -> 23*
    f0(5) -> 5*
    a2() -> 26*
    a0() -> 5*
    b0() -> 5*
    g0(5) -> 5*
    5 -> 16*
    8 -> 22*
    9 -> 5*
    11 -> 17,5
    17 -> 5*
    23 -> 9,5
    26 -> 22*
  problem:
   
  Qed