The school holds a table tennis competition. There are 20 students in the senior group participating. If every two students play one game, how many games will there be in total?
学校举行乒乓球比赛，高年级组有20名同学参加，如果每两名同学比赛一场，一共比赛多少场．
<gadget id="calculator">20 - 1</gadget>
<output>19</output>

<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">19 * 10</gadget>
<output>190</output>

<result>190</result>