Route without some letters

[eluser]someone [/eluser]
Hello!
I'm working on news project and I would like to have clean URLs. I've created table in database for URLs and now I've added routes. This is route which I have now:

Code:

$route['news/(:any)'] = "news/a/$1";

news is controller
a is article which is function in controller

I would like to route all addresses without some letters - c (category), t (tag), ... so if there will be URL like news/c/music, to go next on function and ignore route.

Is this possible?

Thanks! :-)