MAYBE
MAYBE
TRS:
 {
    mark(f(X1, X2, X3)) -> active(f(X1, mark(X2), X3)),
              mark(b()) -> active(b()),
              mark(a()) -> active(a()),
    f(X1, X2, mark(X3)) -> f(X1, X2, X3),
  f(X1, X2, active(X3)) -> f(X1, X2, X3),
    f(X1, mark(X2), X3) -> f(X1, X2, X3),
  f(X1, active(X2), X3) -> f(X1, X2, X3),
    f(mark(X1), X2, X3) -> f(X1, X2, X3),
  f(active(X1), X2, X3) -> f(X1, X2, X3),
   active(f(a(), X, X)) -> mark(f(X, b(), b())),
            active(b()) -> mark(a())
 }
 DUP: We consider a non-duplicating system.
  Trs:
   {
      mark(f(X1, X2, X3)) -> active(f(X1, mark(X2), X3)),
                mark(b()) -> active(b()),
                mark(a()) -> active(a()),
      f(X1, X2, mark(X3)) -> f(X1, X2, X3),
    f(X1, X2, active(X3)) -> f(X1, X2, X3),
      f(X1, mark(X2), X3) -> f(X1, X2, X3),
    f(X1, active(X2), X3) -> f(X1, X2, X3),
      f(mark(X1), X2, X3) -> f(X1, X2, X3),
    f(active(X1), X2, X3) -> f(X1, X2, X3),
     active(f(a(), X, X)) -> mark(f(X, b(), b())),
              active(b()) -> mark(a())
   }
  Fail