YES(?,O(n^1))

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

Proof:
 Bounds Processor:
  bound: 1
  enrichment: match
  automaton:
   final states: {4,3,2}
   transitions:
    c1(6) -> 7*
    b1(5) -> 6*
    b0(1) -> 2*
    c0(1) -> 4*
    a0(1) -> 3*
    f60() -> 1*
    1 -> 5*
    7 -> 3*
  problem:
   
  Qed