Place Ads Between Posts

Hi, I’d like to place ad units between posts on the front page.
I know I have to put the code in the loop.php.
I would like the ads to appear between the three posts that I have on the front page (so two ads). I have only been able to get it so that three ads appear, between posts and also one at the end. How do I make it so that no ads appear at the end, but just in between posts?

Here is my loop.php code:

<?php /* If there are no posts to display, such as an empty archive page */ ?>
<?php if ( ! have_posts() ) : ?>
		<h1><?php _e( 'Not Found', 'ari' ); ?></h1>
		<p><?php _e( 'Apologies, but no results were found for the requested archive. Perhaps searching will help find a related post.', 

'ari' ); ?></p>

<?php endif; ?>

<?php /* Start the Loop. */ ?>
<?php while ( have_posts() ) : the_post(); ?>

<div id="post-<?php the_ID(); ?>" <?php post_class(); ?>>

	<?php if (is_sticky()) echo __( '<h3 class="sticky-label">Featured</h3>', 'ari' ); ?>

<?php the_time('l, F d, Y') ?>
		<a href="<?php the_permalink(); ?>" title="<?php printf( esc_attr__( 'Permalink to %s', 'ari' ), the_title_attribute( 'echo=0' ) ); 

?>" rel="bookmark"><h2><?php the_title(); ?></h2></a>
<?php _e( 'Written by', 'ari' ); ?> <?php the_author() ?> // <?php comments_popup_link( __( 'Leave a comment', 'ari' ), __( 'One comment', 'ari' ), 

__( '% comments', 'ari' ) ); ?>
<br>
<br>
	<?php if ( is_archive() || is_search() ) : // Only display excerpts for archives and search. ?>
			<?php the_excerpt(); ?>
			<p class="meta"><span><a href="<?php the_permalink(); ?>">
	<?php else : ?>
			<?php the_content( __('Read more >>', 'ari' ) ); ?>
			<div class="clear"></div>

			<?php wp_link_pages( array( 'before' => '<div class="page-link">' . __( 'Pages:', 'ari' ), 'after' => '</div>' ) ); ?>

	<?php endif; ?>
<?php if ( count( get_the_category() ) ) : ?>
				<?php endif; ?>
	</div>
	<!--end Post-->
<div class="ad">
<script type="text/javascript"><!--
google_ad_client = "ca-pub-2637633606355131";
/* left ad square */
google_ad_slot = "1791464294";
google_ad_width = 250;
google_ad_height = 250;
//-->
</script>
<script type="text/javascript"
src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
</script>
</div>

		<?php comments_template( '', true ); ?>

<?php endwhile; // End the loop. ?>

<?php /* Display navigation to next/previous pages when applicable */ ?>
<?php if (  $wp_query->max_num_pages > 1 ) : ?>
				<p class="previous"><?php next_posts_link( __( '&larr; Older posts', 'ari' ) ); ?></p>
				<p class="next"><?php previous_posts_link( __( 'Newer posts &rarr;', 'ari' ) ); ?></p>
<?php endif; ?>

Thank you so much!