<nav>
                <?php if (function_exists('wp_nav_menu')) {
                    wp_nav_menu(array('theme_location' => 'main-nav' , 'fallback_cb' => 'default_main_nav' , 'container'  => '' , 'menu_id' => 'main-nav' , 'menu_class' => 'main-nav'));
                } else {
                    default_main_nav();
                } ?>
                <ul id="main-nav" class="main-nav">
    <?php
    wp_list_pages('title_li=&depth=1&include=THE,IDs,OF,THE,PAGES,YOU,WANT,TO,INCLUDE,COMMA,DELIMITED');
    query_posts('cat=23&posts_per_page=1');
    if(have_posts());
    while(have_posts()) :
    the_post();
    ?>
        <li>
            <a href="<?php echo get_permalink(); ?>">LATEST POST</a>
        </li>
    <?php
    endwhile;
    wp_reset_query();
    ?>
</ul>
                <!--/main-nav -->
            </nav>