4 teams play a game, and every two teams play a game, how many games are there in total?
4支球队进行比赛，每两支球队之间都进行一场比赛，一共赛多少场．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

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

<result>6</result>