I’m trying to use single.php to direct to different templates depending on what category the post is in. This works fine when I have one if statement, but when I use two like follows it messes up:

<?php
 $post = $wp_query->post;
 if ( in_category('11') ) {
 include(TEMPLATEPATH . '/single2.php');
} 

 if ( in_category('15') ) {
 include(TEMPLATEPATH . '/single3');
}

else {
 include(TEMPLATEPATH . '/single1.php');
 }
 ?>

Please help!