Alice, Bob and Cindy are good friends. They go shopping together and buy the same. However, they don't bring the same units money with themselves so one of them suggests that the one with the most money should borrow 1 unit money to someone else with equal probability. That is to say, if they have $x, y, z(x \ge y \ge z)$ units money separately, the one with $x$ units money (if multiple people have the most then they decide one should borrow with equal probability) will give 1 unit to one of his/her friends with equal probability. After that, they have $x - 1, y + 1, z$ or $x - 1, y, z + 1$ units money.
This act will last until everyone has the same units money. Three smart guys want to know the expected times of this act or if this situation will never come.