In the monthly football match held in the third grade of the National People’s University Attached Primary School, 12 classes played a single round-robin match, that is, there was a match between every two classes, and how many matches were there in total.
在人大附小三年级举行的足球月赛中，12个班进行单循环赛，即每两个班之间都要进行一场比赛，一共要赛多少场．
<gadget id="calculator">12 - 1</gadget>
<output>11</output>

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">11 * 6</gadget>
<output>66</output>

<result>66</result>