people each get a message at the same time. Moreover, any two people get different information. They use the phone to tell each other all the news they know. Each phone call takes exactly 3 minutes. What is the minimum number of minutes required for everyone to know all the news.
8个人每人同时得到一条消息．而且任意两人所得消息不同，他们两两用电话相互告诉对方自己所知的全部消息，每次电话恰好用3分钟．为使每人都知道所有消息，至少需多少分钟．
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<result>9</result>