There are 7 athletes, if every two people shake hands once, how many times will they shake hands in total?
有7名运动员，如果每两人握一次手，一共握多少次手．
<gadget id="calculator">7 - 1</gadget>
<output>6</output>

<gadget id="calculator">7 / 2</gadget>
<output>7/2 = around 3.5</output>

<gadget id="calculator">6 * (7/2)</gadget>
<output>21</output>

<result>21</result>