Atuomatically add adsense in posts but…

Hello everyone,
Can I add this option to exclude some posts

<?php if (is_single(’666')) {
}
else { ?>

<p>Show this everywhere!</p>

<?php } ?>

with this code

<?php
  $content = apply_filters('the_content', $post->post_content);  //get the post content store in $content
  $save = explode("</p>", $content);  //Separate the content into <p> blocks
  $tcount=0; //this is count for number of <p> blocks
  $adon=0;  //this is a variable so you don't show ads more than once.
  foreach($save as $item) {
    echo $item;  //print the <p> block
    echo "</p>";
    if(preg_match('/<p> /',$item)==0 && $tcount>=1 && $adon==0) {
                                $adon=1;
?>
ADSENSE HERE
<?php
    }
 if(preg_match('/<p> /',$item)==0 && $tcount>=4 && $adon==1) {
                                $adon=2;
?>
ANOTHER ADSENSE IF YOUR POST HAVE MORE THEN 4 PARAGRAPHS
<?php
   }
   $tcount++;
 }
?>

Is this possible?

Thank you.