301 permanent redirect with Code Igniter

[eluser]sojic[/eluser]
I want to add 301 redirect non www to www

Code:

RewriteEngine On
RewriteCond %{HTTP_HOST} ^example.com
RewriteRule (.*) http://www.example.com/$1 [R=301,L]

How to "combine" this with .htaccess code igniter rewrites? In the beginning, end.... some another flag???

.htaccess with Code Igniter which I use

Code:

RewriteCond %{REQUEST_URI} ^system.*
    RewriteRule ^(.*)$ /index.php/$1 [L]

    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule ^(.*)$ index.php/$1 [L]

ErrorDocument 404 /index.php