For every 2 people shaking hands, how many times will 3 people shake hands in total?
每2人握一次手，3个人一共握多少次手．
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">3 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">2 * (3/2)</gadget>
<output>3</output>

<result>3</result>