Кнопка плюс минус один Instantshop

<td><input type="text" class="amount"....</td>

<td><span class="minus_qty">-</span><input type="text" class="amount" name="qty" value="1" size="3" style="text-align:center"/><span class="plus_qty">+</span></td>

 
<script type="text/javascript" >
        {literal}
                         $(document).ready(function() {
                         $('.minus_qty').click(function () {
                          var $input = $(this).parent().find('input');
                          var count = parseInt($input.val()) - 1;
                          count = count < 1 ? 1 : count;
                          $input.val(count);
                          $input.change();
                          return false;
                         });
                        $('.plus_qty').click(function () {
                        var $input = $(this).parent().find('input');
                        $input.val(parseInt($input.val()) + 1);
                        $input.change();
                        return false;
                        });
                        });
        {/literal}
</script>
 

 
  .minus_qty {
   width:11px;
   height:11px;
   background:#f4f4f4;
   border-radius:4px 0 0 4px;
-webkit-border-radius:4px 0 0 4px;
-moz-border-radius:4px 0 0 4px;
   padding:3px 5px 3px 5px;
   border:1px solid #d5d5d5;
cursor: pointer;
}
.plus_qty {
   width:11px;
   height:11px;
   background:#f4f4f4;
   border-radius: 0 4px 4px 0;
-webkit-border-radius: 0 4px 4px 0;
-moz-border-radius: 0 4px 4px 0;
   padding:3px 5px 3px 5px;
   border:1px solid #d5d5d5;
cursor: pointer;
}
 
 
input.amount {
height: 20px;
line-height: 20px;
border-top: 1px solid #d5d5d5;
border-bottom: 1px solid #d5d5d5;
border-left:0;
border-right:0;
}