20 badminton players participate in a singles match, paired in pairs for a single round robin match, how many games will the champion have to play in total?
20名羽毛球运动员参加单打比赛，两两配对进行单单循环赛，那么冠军一共要比赛多少场．
<gadget id="calculator">20 - 1</gadget>
<output>19</output>

<result>19</result>