@me%2==0

{dede:arclist row='4' flag='p' titlelen='20' typeid='59'}

            <li [field:global runphp='yes' name=autoindex]if(@me%2==0){@me="class='floatl'";}else {@me="class='floatr'";}[/field:global] ><a href="[field:arcurl/]" title="" target="_blank"><img src="[field:litpic/]" width="144" height="105" /><p>[field:title/]</p><em></em></a>

       {/dede:arclist}