Four classes of the fourth grade will have a football match, and there will be a game between every two classes, so how many games will be played in total.
四年级4个班要进行足球比赛，每两个班之间要赛一场，那么一共需要进行多少场比赛．
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">3 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">4 * (3/2)</gadget>
<output>6</output>

<result>6</result>