TRS:
 {a__f(f(a())) -> c(f(g(f(a())))),
    mark(f(X)) -> a__f(mark(X)),
     mark(a()) -> a(),
    mark(c(X)) -> c(X),
    mark(g(X)) -> g(mark(X)),
       a__f(X) -> f(X)}
 MPO:
  Prec:
   a__f > c, 
   a__f > f, 
   a__f > g, 
   mark > a__f, 
   mark > g
   empty
  Strict:
   {}
   Weak:
    {}
  Qed