There are 6 members in a certain interest group. In each meeting, if every two people shake hands once, how many times will they shake hands in total?
某兴趣小组共6名队员，在每次见面会上，如果每两人握一次手，一共要握多少次手．
<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>