server removes duplicate slashes

Question

server removes duplicate slashes from url, if i try to get http://mysite.com/a//b/

with .htaccess:

RewriteEngine On

RewriteBase /

RewriteCond %{REQUEST_FILENAME} !-f

RewriteCond %{REQUEST_FILENAME} !-d

RewriteRule ^(.*)$ /index.php?r=$1 [L]

string that comes to php script is "a/b/" but expected "a//b/" how can i disable removing slashes from url?