dede在列表页调用文章时如何给列表加上序号

<ul class="txt">
  {dede:arclist orderby=pubdate type='commend.' titlelen='26' row='10' channel=3}
  <li>[field:global runphp='yes' name=autoindex]
     $a="<span class='num active'>";
     $b="</span>";
     $c="<span class='num'";
     if (@me > 3) @me = $c.@me.$b;
     else @me = $a.@me.$b;
     [/field:global]
     <span class="tit">
         <a title="[field:title/]" href="[field:filename/]">[field:title/]</a>
      </span><li>
   {/dede:arclist}
   </ul>