Rewriting URL rule, example like StackOverflow

What would be the apache rewrite url to extract the id number (434376) from this url?

http://stackoverflow.com/questions/434376/unique-url-slug

something like

R开发者_开发技巧ewriteEngine On  
RewriteRule ^questions/([0-9]+)/?$([A-Za-z0-9-]+)   post.php?post_id=$1 [NC,L]  

...but it doesnt work on my site...any tips?

thanks

---

Tested:

RewriteRule ^questions/([0-9]+)/?.*$   rewrite.php?post_id=$1 [NC,L]

---

Well if the / is optional it probably should be:

RewriteRule ^questions/([0-9]+)/?([A-Za-z0-9-]+)?/?$   post.php?post_id=$1 [NC,L]

Let me know if it works..