There are 56 students in the class, if every two people shake hands once, how many times should they shake hands in total?
全班56名同学，如果每两个人握一次手，一共要握多少次手．
<gadget id="calculator">56 - 1</gadget>
<output>55</output>

<gadget id="calculator">55 / 2</gadget>
<output>55/2 = around 27.5</output>

<gadget id="calculator">56 * (55/2)</gadget>
<output>1_540</output>

<result>1_540</result>