What is the redirect code when redirecting to the appropriate language version of the page?

Question

Search Engine Optimization

Good afternoon.
There are two language versions of the site: site.com/ru and site.com/en. When accessing the site without specifying the site.com/ language, the Accept-Language header is checked and the user is directed to the version that suits him.
Tell me, with what HTTP code you need to carry out this redirect, so as not to get in the ass from the search engines?
Thank you.