There are 5 children playing a round-robin chess game. To select the champion and the runner-up, how many games are needed at least.
有5位小朋友进行象棋单循环比赛，要选出冠军和亚军，最少需要多少场比赛．
<gadget id="calculator">5 - 1</gadget>
<output>4</output>

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

<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<result>10</result>