The school holds chess competitions, which are divided into three categories: chess, go and military chess. Each student can participate in two of them at most. According to the number of applicants, the school decides to distribute prizes to the top 9 players in Xiangqi, the top 10 players in Go and the top 11 players in Army Chess. I would like to ask: at least how many people get prizes?
学校举行棋类比赛，分为象棋、围棋和军棋三项，每人最多参加其中两项．根据报名的人数，学校决定对象棋的前9名、围棋的前10名和军棋的前11名发放奖品．请问：最少有几人获得奖品？
<gadget id="calculator">9 + 10 + 11</gadget>
<output>30</output>

<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<result>15</result>