Ampliar largura do primeiro post na index.php

<?php get_header(); ?>
<main class="wrap">
  <section class="content-area content-thin">
<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
      <article class="article-loop">
        <header>
			<?php 	if ( has_post_thumbnail() ) { ?>
		<div class='post-thumb'>
				<a href="<?php the_permalink();?>" >
				<?php the_post_thumbnail(''); ?>
				</a>
		</div>
			<?php the_category(); ?>
          <h2><a href="<?php the_permalink(); ?>" title="<?php the_title_attribute(); ?>"><?php the_title(); ?></a></h2>      
        </header>    
	<?php } ?>
      </article>
<?php endwhile; else : ?>
      <article>
        <p>Sorry, no posts were found!</p>
      </article>
<?php endif; ?>
  </section><?php get_sidebar(); ?>
</main>
<?php get_footer(); ?>

<?php if (have_posts()) : ?>
<?php $count = 0; ?>
<?php while (have_posts()) : the_post(); ?>
<?php $count++; ?>
<?php if ($count == 1) : ?>

<!-- Aca tendrias que poner el diseño que sea mas ancho. -->
 <article class="article-loop"> 
        <header> 
            <?php     if ( has_post_thumbnail() ) { ?> 
        <div class='post-thumb'> 
                <a href="<?php the_permalink();?>" > 
                <?php the_post_thumbnail(''); ?> 
                </a> 
        </div> 
            <?php the_category(); ?> 
          <h2><a href="<?php the_permalink(); ?>" title="<?php the_title_attribute(); ?>"><?php the_title(); ?></a></h2>       
        </header>     
    <?php } ?> 
      </article> 



<?php else : ?>
 
<!-- Aca el que ya tenes -->

 <article class="article-loop"> 
        <header> 
            <?php     if ( has_post_thumbnail() ) { ?> 
        <div class='post-thumb'> 
                <a href="<?php the_permalink();?>" > 
                <?php the_post_thumbnail(''); ?> 
                </a> 
        </div> 
            <?php the_category(); ?> 
          <h2><a href="<?php the_permalink(); ?>" title="<?php the_title_attribute(); ?>"><?php the_title(); ?></a></h2>       
        </header>     
    <?php } ?> 
      </article> 



  <?php endif; ?>
<?php endwhile; else : ?> 
      <article> 
        <p>Sorry, no posts were found!</p> 
      </article> 
<?php endif; ?>