How to Insert Two Ads into Post Content (Without a Plugin)

I am trying to avoid using plugins that say they can do this.

I’m currently using the code below. It works great, and I’m able to set it to display a single ad unit, left aligned after the second paragraph.

Some posts on this site run as long as 4,000 words so I’d like to display a second DIFFERENT ad unit, right aligned at the 10th or 12th paragraph.

How do I modify this code to that?

<?php
    $paragraphAfter= 1; //display after the first paragraph
    $content = apply_filters(‘the_content’, get_the_content());
    $content = explode(“</p>”, $content);
    for ($i = 0; $i <count($content); $i ) {
    if ($i == $paragraphAfter) { ?>

    <div class="alignleft">Ad Code Here</div>

    <?php }
    echo $content[$i] . “</p>”;
    } ?>