There are 6 teams participating in a sports competition. If a round-robin system is adopted (every two teams compete one game), how many games will there be in total?
一次体育比赛，有6个队参加．如果采用循环赛制(每两队比一场)，那么一共要比几场？
<gadget id="calculator">6 - 1</gadget>
<output>5</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">6 * (5/2)</gadget>
<output>15</output>

<result>15</result>