First lesson

If you are a US citizen, trying to travel to Russia, you should know that you can only stay, as a tourist, for 30 days. You cannot stay for 31 days. So the first thing you need to do, when buying an airplane ticket, is to count the days, so that you are not staying longer than 30 ... inclusive of your arrival & departure days.

Aeroflot will sell you a ticket for 31 days, and charge you $150 to change the ticket, when you learn your lesson!