Customizing the permalink page

Hello everybody! First of all, my english is really poor. I’m so sorry. But I have a great problem.

I need to put a class attribute (with the same name) to permalink page, but I haven’t found where I must insert the code. My

This is an example of I want:

<ul class="menu">
    <li><a class="clase">About me</a></li>
    <li><a class="clase">Contact</a></li>
    <li><a class="clase">Archive</a></li>
</ul>

I think I must modify this (put the class attribut to the permalink pages) inside the code of WordPress, but I use K2 theme (for more information).

Any idea?