There are 15 leaders participating in the "Chuangqiang" work meeting. Every two people shake hands once. How many times do they need to shake hands in total?
有15位领导参加"创强"工作会议，每两人握一次手，共需握多少次手．
<gadget id="calculator">15 - 1</gadget>
<output>14</output>

<gadget id="calculator">15 / 2</gadget>
<output>15/2 = around 7.5</output>

<gadget id="calculator">14 * (15/2)</gadget>
<output>105</output>

<result>105</result>