There are 10 children, and every 2 people take a group photo, how many photos should be taken in total?
有10个小朋友，每2人照一张合影，一共要照多少张照片？
<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">9 * 5</gadget>
<output>45</output>

<result>45</result>