A round-robin game is played with n players, that is, there is a game between any two players. The winner gets two points, the tie gets one point, and the loser gets no points. After the game, the top four get 8, 7, 5, 4 points respectively, n=how much.
n名棋手进行单循环比赛，即任两名棋手间都比赛一场．胜者得两分，平局各得一分，负者没分．比赛完毕后，前四名各得8、7、5、4分，n=多少．
<result>6</result>