A set of n dice is thrown. All those that land on six are put aside, and theothers are again thrown. This is repeated until all the dice have landed on six. LetN denote the number of throws needed. (For instance, suppose that n = 3 and thaton the initial throw exactly two of the dice land on six. Then the other die will bethrown, and if it lands on six, then N = 2.) Let m n = E[N].