function shorturl(){
    global $post;
    is_single() == true ? $out = get_bloginfo('url')."/".$post->ID : $out = get_bloginfo('url')."/";
    echo $out;
} 
add_action( 'generate_rewrite_rules', 'custom_rewrite_rules' );
function custom_rewrite_rules( $wp_rewrite )
{
$newRules = array();
$newRules[ '([0-9]+)$' ] = 'index.php?p=' . $wp_rewrite->preg_index( 1 );
$wp_rewrite->rules = $newRules + $wp_rewrite->rules;
return $wp_rewrite;
}