There are 20 players participating in a chess game (regardless of gender), each player will play one game, how many games will be played in total.
有20名运动员参加的国际象棋比赛(不分男女)，每两人之间都要赛1场，总共要赛多少场．
<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>