Automatic redirect of any subdomain to the domain name folder

Question

Domain name market

Good afternoon,
to redirect a subdomain to a site folder, the name of which also matches the subdomain name, I use:

RewriteEngine on
RewriteBase /
RewriteCond %{HTTP_HOST} ^subdomain\.mysite\.ru$
RewriteCond %{REQUEST_URI} !/subdomain/
RewriteRule ^(.*)$ /subdomain/$1 [L]

but there can be hundreds of such subdomains. How can this process be automated?
Get the name of the subdomain: RewriteCond %{HTTP_HOST} ^((.*)\.)mysite\.ru$
What should the subdomain be replaced with?
Thank you.

Answer 1

Working option:

RewriteEngine On
RewriteRule ^([a-zA-Z]+)/ - [L]
RewriteCond %{HTTP_HOST} ^(.*)\.mysite\.ru$
RewriteCond %{DOCUMENT_ROOT}/%1%{REQUEST_URI} -d
RewriteRule [^/]$ %{REQUEST_URI}/ [R,L]
RewriteCond %{HTTP_HOST} ^(.*)\.mysite\.ru$
RewriteRule (.*) %1/$1 [L,QSA]

This option didn't work.

RewriteEngine On
RewriteCond %{HTTP_HOST} !^www.mysite.ru$
RewriteCond %{HTTP_HOST} ^((.*)\.)mysite.ru$
RewriteRule ^/(.*) /%2/$1