How to check a string for the absence of a number of letters in RewriteCond (regular expressions, htaccess)?

Question

PHP

There is a RewriteCond %{REQUEST_URI} condition. In the requested string (domain.com /ru/apartment/228 ), we need to check for the presence of "/ru/" at the beginning (domain.com /apartment/228 ) and if it is not there, then we use RewriteRule... Tried with !ru and all sorts of nonsense like !^[^\/en\/]

Answer 1

^(?!ru)

Answer 2

RewriteCond %{REQUEST_URI} !^.*\.ru$
But if you also need this option
RewriteCond %{REQUEST_URI} !^.*\.(ru\|ru\/)$