You are a young man, who came in a shop to buy some DVDs. But you found out that you had not enough money to buy even one disc. Fortunately the assistant is a gambler and he suggests you another way to get DVDs - to play shell game. Your goal is to guess which shell holds the ball, when all shells are mixed. Make a bet and when shells will stop you shall choose the shell, which contains (in your opinion) a ball.
