Each of the 10 people shook hands with each other one by one, how many times in total.
10个人每人都与别人一一握手，一共握多少次．
<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>