There are 6 athletes, if every two shake hands once, how many times will they shake hands in total?
有6名运动员，如果每两人握一次手，一共握多少次手．
<gadget id="calculator">6 - 1</gadget>
<output>5</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">6 * (5/2)</gadget>
<output>15</output>

<result>15</result>