20 teams participate in a table tennis team competition. If there is a round robin competition, how many games are needed?
20个队参加乒乓球团体赛，如果进行循环赛，需要比赛多少场．
<gadget id="calculator">20 - 1</gadget>
<output>19</output>

<gadget id="calculator">19 / 2</gadget>
<output>19/2 = around 9.5</output>

<gadget id="calculator">20 * (19/2)</gadget>
<output>190</output>

<result>190</result>