For non-cyrillic readers, thats Sakhalin. Curiously, the
Airport Code lookup on this site doesn't include UUS (where do I report that bug?), but it is Yuzhno-Sakhalinsk Airport.
Wiki suggests that Seoul and Sapporo are the only places outside Russia with scheduled service, but I've no idea how current that is. Personally I would go via Seoul even from London so that I could use Asiana and avoid Russian airlines.