drop: function (event, ui)
    {
        var draggable      = $(ui.draggable)
          var droppable      = $(this)
           var draggableClass = draggable.attr('class')
          var droppableClass = droppable.attr('class');

        droppable.append(draggable.text());
        draggable.attr('class', droppableClass);
        droppable.attr('class', draggableClass);
        draggable.empty();
    }