MAYBE
MAYBE
TRS:
 {
       a__f(X, X) -> a__f(a(), b()),
     a__f(X1, X2) -> f(X1, X2),
           a__b() -> a(),
           a__b() -> b(),
        mark(a()) -> a(),
        mark(b()) -> a__b(),
  mark(f(X1, X2)) -> a__f(mark(X1), X2)
 }
 DUP: We consider a non-duplicating system.
  Trs:
   {
         a__f(X, X) -> a__f(a(), b()),
       a__f(X1, X2) -> f(X1, X2),
             a__b() -> a(),
             a__b() -> b(),
          mark(a()) -> a(),
          mark(b()) -> a__b(),
    mark(f(X1, X2)) -> a__f(mark(X1), X2)
   }
  Fail