I have searched everywhere for this answer, and the answers that have been posted do not fit my specific situation as it gives me 404 errors, and I\'m not sure why.
Apache removes multiple slashes inside the path. And as you’re already mentioned, you can solve this by inspecting the request line in THE_REQUEST:
RewriteCond %{THE_REQUEST} ^[A-Z]+\ /c/([^?\ ]+)/? RewriteRule ^c/ /c.php?url=%1