12 students participated in the celebration, each shook hands with everyone else, how many times did they shake hands in total?
12个同学参加庆祝活动，每个人都与其他人握一次手，他们一共握多少次手？
<gadget id="calculator">12 - 1</gadget>
<output>11</output>

<gadget id="calculator">11 / 2</gadget>
<output>11/2 = around 5.5</output>

<gadget id="calculator">12 * (11/2)</gadget>
<output>66</output>

<result>66</result>