[jQuery] how i can get the "id" of the dropped tag

[Smirnoff]

how i can get the "id" of the dropped tag in this code :

  <script type="text/javascript">
  $(document).ready(function(){
    $("#draggable").draggable();
    $("#droppable").droppable({
      drop: function() {
                 alert($(" ??? "));

                }
    });
  });
  </script>


the tags is :
<ul>
   <li id="item_1">
   <li id="item_2">
   <li id="item_3">
</ul>

thanks.