There are 6 people playing table tennis, each of them will play one game, how many games will there be in total?
6个人进行乒乓球比赛，每两人之间都要赛一场，一共要比赛多少场．
<gadget id="calculator">6 - 1</gadget>
<output>5</output>

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

<gadget id="calculator">5 * 3</gadget>
<output>15</output>

<result>15</result>