During the sports meeting, 4 classes in the first grade will have a tug-of-war competition, and there will be a tug-of-war between every two classes. How many games will there be in total?
运动会期间，一年级4个班进行拔河比赛，每两个班之间都要拔一场，一共要拔多少场．
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<result>6</result>