<?php
add_filter('the_content', 'google_ads');
function google_ads($content){
  if(is_page()||is_single()){
    ob_start();
?>
<div class="google center">
<!--Google AdSense Code HERE-->
</div>
<?php
    $content = ob_get_contents().$content;
    ob_end_clean();
  }
  return $content;
}
?>