What will be the apache rewrite hyperlink to extract the id number (434376) out of this url?

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

something similar to

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

...however it does not focus on my website...any tips?

thanks

Examined:

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

Well when the / is optional it most likely ought to be:

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

Tell me whether it works..