Posts from all Categories except 2

I have the following code snippet…

<?php
$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
$args= array(
	'cat' => 21,
	'paged' => $paged
);
query_posts($args);
if (have_posts()) :
?>

This code works great – showing all the posts in category #21.

I need to change it though…
What I need now is to show posts from all categories EXCEPT categories #1 & 5.

Can someone please show me what would need to be modified in my code to do this?