MAYBE
MAYBE
TRS:
 {
       a__f(X) -> f(X),
  a__f(f(a())) -> a__f(g(f(a()))),
    mark(g(X)) -> g(mark(X)),
    mark(f(X)) -> a__f(X),
     mark(a()) -> a()
 }
 DUP: We consider a non-duplicating system.
  Trs:
   {
         a__f(X) -> f(X),
    a__f(f(a())) -> a__f(g(f(a()))),
      mark(g(X)) -> g(mark(X)),
      mark(f(X)) -> a__f(X),
       mark(a()) -> a()
   }
  Fail