How use route in Codeigniter

[eluser]memVN[/eluser]
@weboap: thank you but I mean that link http://demo.com/article/12/abc with "article" is a controller, and now I want to change it to http://demo.com/bai-viet-12-a-b-c, it's mean change controller "article" to "bai-viet"
I was trying use to Regular Expressions ([a-zA-Z0-9_-]+) to do but not successfully