TRS:
 {   a__f(X, g(X), Y) -> a__f(Y, Y, Y),
            a__g(b()) -> c(),
               a__b() -> c(),
  mark(f(X1, X2, X3)) -> a__f(X1, X2, X3),
           mark(g(X)) -> a__g(mark(X)),
            mark(b()) -> a__b(),
            mark(c()) -> c(),
     a__f(X1, X2, X3) -> f(X1, X2, X3),
              a__g(X) -> g(X),
               a__b() -> b()}
 Fail