Error in jquery

What error could there be in the line with li draggable? (As the console says in the browser).

<script> $("li").draggable({ revert: true, scroll: false, helper: 'clone' }); $("#city-second").droppable({ drop: function (event, ui) { this.value = $(ui.draggable).attr('id'); } }); </script> 

From the above list of cities, each of which is enclosed in a li tag, it is necessary to make their names drag and drop into a line and a line, respectively, filled with the names of these cities.