TIMEOUT
MAYBE
Trs:
 {       f(g(x, y)) -> g(y, g(f(f(x)), a())),
  g(e(), g(e(), x)) -> g(d(), g(c(), x)),
  g(c(), g(c(), x)) -> g(e(), g(d(), x)),
  g(d(), g(d(), x)) -> g(c(), g(e(), x)),
            g(x, x) -> g(a(), b())}
 Open