TRS:
 {f(g(x)) -> g(g(f(x))),
  f(g(x)) -> g(g(g(x)))}
 POP*:
  Precedence:
  f > g
  empty
  
Normal:
   pi(f) = [1]
  
Safe:
   pi(g) = [1]
  
Predicative System:
   {f(g(;x);) -> g(;g(;f(x;))),
    f(g(;x);) -> g(;g(;g(;x)))}
  Qed