Uncle Zeng, Aunt Wen, and Uncle Guan came to Dr. Huang’s clinic to see a doctor at the same time (only Dr. Huang can see patients in the clinic), and the time they needed to see a doctor was 9 minutes, 11 minutes, and 6 minutes respectively. What is the minimum sum of waiting time for the three of them to see a doctor?
曾大爷、文阿姨、官叔叔三人同时来到黄医生诊所看病(诊所里只有黄医生能给病人看病)，他们看病需要的时间分别是9分钟、11分钟、6分钟．他们三人看病等候时间的总和最少是多少分钟．
<gadget id="calculator">6 * 3</gadget>
<output>18</output>

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

<gadget id="calculator">11 * 1</gadget>
<output>11</output>

<gadget id="calculator">18 + 18 + 11</gadget>
<output>47</output>

<result>47</result>