约瑟夫环问题，一群人围在一起做成环状，从某个编号开始报数，数到某个数的时候，此人出列，下一个人重新报数，一直循环，直到所有人出列，约瑟夫环结束。-Josephus problem, a group of people get together to make a ring,　a number countin, count to a number of time, this person out of the line, the next person to re-report the number of loops until all of the columns Joseph loop ends.