Li Ming, Zhang Qiang, Wang Fang, Liu Yang, Song Hong, and Han Gang held a table tennis match. If each of them had to play a game, how many games did they play in total?
李明、张强、王芳、刘洋、宋红、和韩刚6人举行乒乓球比赛，如果每两人都要进行一场比赛，那么他们一共进行了多少场比赛．
<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>