urlrewrite路径参数获取问题

<rule>
   <note>***</note>
   <from>/([a-z]{2,25})/((([a-z]{2,25})/){0,1})((pagindex([0-9]+)/){0,1})$</from>
   <to>project!fyShow.action?url1=$1&amp;curindex=？</to>
</rule>

我要取到pagindex后面跟着的数字  请问？处应该怎么写