10 classmates, everyone should shake hands once, at least how much. Second-rate.
10个同学，每人都要握一次手，至少要握多少．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>