students line up to fetch water, there is only one faucet, student A takes 2 minutes, student B takes 3 minutes, student C takes 5 minutes, they all finish fetching water, what is the minimum sum of the waiting time?
3名同学排队打水，只有一个水龙头，甲同学需要2分钟，乙同学需要3分钟，丙同学需要5分钟，他们都打完水，等待时间的总和最少是多少分钟．
<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<gadget id="calculator">6 + 6 + 5</gadget>
<output>17</output>

<result>17</result>