Google autocomplete js script is not workin

I have a website for appointment booking. I want to put google maps autocomplete city option with the search option. Here is the script I using (along with my api)

<script type="text/javascript">
      function activatePlacesSearch(){
        var input document.getElementById('city');
        var autocomplete = new google.maps.places.Autocomplete(input);
      }
    </script>
    <script type="text/javascript" src="http://ift.tt/2yUpnMW"></script>

The id of my input filed is city. But after placing this script also it do not suggest any autofill option. Need help. Thankyou.