If two people meet and shake hands once, according to this rule, how many times do three people shake hands when they meet?
两人见面握一次手，照这样规定，3人见面握多少次手．
<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>