There are 8 students competing, and there is a competition between each two students, how many games are needed in total.
有8名同学进行比赛，每两人之间都要进行一场比赛，一共需要多少场．
<gadget id="calculator">8 - 1</gadget>
<output>7</output>

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">7 * 4</gadget>
<output>28</output>

<result>28</result>