Magic Cup

Three cups, and one of them contains yellow ball. Can you say which is it? Things are getting more complicated, though. Before you will be able to say your opinion, the position of cups will change including the one with the ball. So memorize the cup with the ball, and watch this cup as it changes positions with other cups. Once the swapping stops, reveal of the cups, and see whether you chose the right one. How many rounds will you manage to guess the right cup? Have fun.