There are 6 participating teams in the primary school basketball meeting. If there is a competition between every two teams, how many games will there be in total?
小学要举行篮球运动会，共有6个参赛队，如果每两个队之间都要举行一场比赛，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>