YES(?,O(n^1))

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

Proof:
 Bounds Processor:
  bound: 2
  enrichment: match
  automaton:
   final states: {4,3,2}
   transitions:
    b1(9) -> 10*
    b1(8) -> 9*
    c2(12) -> 13*
    c2(11) -> 12*
    c2(13) -> 14*
    a0(1) -> 2*
    b0(1) -> 3*
    c0(1) -> 4*
    f60() -> 1*
    1 -> 8*
    8 -> 11*
    10 -> 2*
    14 -> 10*
  problem:
   
  Qed