<?php $firstPost = 1; ?>
<?php while( have_posts() ): the_post(); ?>

	<?php if ( $firstPost == 1 ){ ?>
    	<div class="full-width">
    		<?php 
                the_content(); 
                $firstPost = 5;
            ?>
        </div>
    <?php } else ?>
    <?php echo $firstPost; ?>    
    
<?php endwhile;  ?>