The interest group held a checkers competition. A total of 12 students participated. The first round was divided into 6 groups for a single round-robin knockout match. The remaining 6 students in the second round had to compete once for every two students. How many games.
兴趣小组举办跳棋比赛，一共有12名同学参加，第一轮分6组进行单循环淘汰赛，第二轮剩下的6名同学之间每两名同学都要比赛一次，一二轮一共要进行多少场比赛．
<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<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>

<gadget id="calculator">15 + 6</gadget>
<output>21</output>

<result>21</result>