减法游戏。两名对手交替从某一个给定的总数减去一个数，每个对手每次只能减去1或2，谁第一个把总数减到0获胜。-Subtraction game.Alternate two opponents a given total minus a number, each opponent can be minus 1 or 2 at a time, who win the first cuts total to 0.