There are 6 students in the badminton team who compete within the team. If every two students compete with each other, how many games will there be in total?
羽毛球队6名同赛学进行队内比赛，如果每两位同学之间都进行比赛，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>