TRS:
 {f(x, a(b(y))) -> f(a(b(x)), y),
  f(x, b(c(y))) -> f(b(c(x)), y),
  f(x, c(a(y))) -> f(c(a(x)), y),
     f(a(x), y) -> f(x, a(y)),
     f(b(x), y) -> f(x, b(y)),
     f(c(x), y) -> f(x, c(y))}
 Fail