htaccess rule question

I have a htaccess which looks like this:

RewriteEngine on
RewriteCond $1 !^(index\.php|images|css|js|robots\.txt|favicon\.ico)
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ ./index.php/$1 [QSA]
RewriteRule ^$ /naujausios [L,R] 

And I'm not sure where to put this:

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

for it to work properly - I tried a few modifications to the keys at the end, without success - I just end up with a 500 response. Thanks for your help!

I had conflicts wherever I put it, but the solution was to put the www bit rewrite at the very top just after RewriteEngine on