Add Advertisement after 1st post in Genesis

functions.php

add_action('genesis_after_post', 'ad_after_first_post');
function ad_after_first_post() {
  global $wp_query;
  if( !is_singular && 0 == $wp_query->current_post ) { ?>
    <div id='div-gpt-ad-1442795039305-2'>
      <script type='text/javascript'>
        googletag.cmd.push(function() { googletag.display('div-gpt-ad-1442795039305-2'); });
      </script>
    </div>
<?php }
}