There is a chess game with less than 20 players. Each chess player plays exactly one game with other chess players. The winner gets 2 points, the loser gets 0 points, and the draw gets 1 point. Now we know female chess players There are at least 3, the male chess player is 3 times that of the female chess player, but the total score of the male chess player is 7 times that of the female chess player, so how many rounds can the female chess player beat the male chess player at most?
有一场少于20人参加的棋赛，每位棋手都与其它棋手恰好各对局一次，胜者得2分，负者得0分，和局各得1分，现知女棋手至少有3位，男棋手是女棋手的3倍，但男棋手总分是女棋手总得分的7倍，那么女棋手胜男棋手至多有多少局．
<gadget id="calculator">30 - 12</gadget>
<output>18</output>

<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<result>9</result>