MAYBE
MAYBE
TRS:
 {
                        app(app(map(), f), nil()) -> nil(),
      app(app(map(), f), app(app(cons(), x), xs)) ->
  app(app(cons(), app(f, x)), app(app(map(), f), xs)),
                    app(app(append(), nil()), xs) -> xs,
  app(app(append(), app(app(cons(), x), xs)), ys) ->
  app(app(cons(), x), app(app(append(), xs), ys)),
                             app(concat(), nil()) -> nil(),
           app(concat(), app(app(cons(), x), xs)) ->
  app(app(append(), x), app(concat(), xs)),
          app(flatten(), app(app(node(), x), xs)) ->
  app(app(cons(), x), app(concat(), app(app(map(), flatten()), xs)))
 }
 DUP: We consider a duplicating system.
  Trs:
   {
                          app(app(map(), f), nil()) -> nil(),
        app(app(map(), f), app(app(cons(), x), xs)) ->
    app(app(cons(), app(f, x)), app(app(map(), f), xs)),
                      app(app(append(), nil()), xs) -> xs,
    app(app(append(), app(app(cons(), x), xs)), ys) ->
    app(app(cons(), x), app(app(append(), xs), ys)),
                               app(concat(), nil()) -> nil(),
             app(concat(), app(app(cons(), x), xs)) ->
    app(app(append(), x), app(concat(), xs)),
            app(flatten(), app(app(node(), x), xs)) ->
    app(app(cons(), x), app(concat(), app(app(map(), flatten()), xs)))
   }
  Fail