The existing 12 teams are divided into 3 groups to participate in the volleyball competition. There is a competition between every two teams in the group, so how many games will the 12 teams have in total?
现有12支球队分成3个小组参加排球比赛．小组内每两队之间都要比一场，那么12支队一共要比赛多少场．
<gadget id="calculator">12 / 3</gadget>
<output>4</output>

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

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

<gadget id="calculator">6 * 3</gadget>
<output>18</output>

<result>18</result>