There are 13 children in a row. There are 3 people in front of Qiangqiang, and how many people are behind Qiangqiang?
一排小朋友一共13人，排在强强前面的有3人，排在强强后面的有几人？
<gadget id="calculator">13 - 3 - 1</gadget>
<output>9</output>

<result>9</result>