Dynamic .htaccess redirect

I'm trying to create an .htaccess redirect so that an folder will redirect to its proper page.

For example... http://exampl开发者_如何转开发e.com/contactus/help.html will redirect to http://example.com/contact-us/help.html or http://example.com/contactus to http://example.com/contact-us

<IfModule mod_rewrite.c>
  RewriteCond %{HTTP_HOST} ^example\.com/contactus/(.+)$ [NC]
  RewriteRule ^ http://example\.com/contact-us/%1 [R=301,L]
</IfModule>