约瑟夫环（Josephus）问题：古代某法官要判决N个犯人的死刑，他有一条荒唐的法律，将犯人站成一个圆圈，从第S个人开始数起，每数到第D个犯人，就拉出来处决，然后再数D个，数到的在处决……知道剩下的最后一个可赦免。-Central Joseph (Josephus) Question: Ancient N a judge to sentence a prisoner to death, he has a ridiculous law, prisoners stand in a circle, S from the beginning of a number of individuals, each of the first D of the number of prisoners, on the pull out the execution, and then the number of D, and the number of executions of the ... ... know that the last remaining of a pardon.