9 students play a Chinese chess match. If every two players play one game, how many games will they play in total?
9位同学进行中国象棋比赛，如果每两人赛一场，一共要赛多少场．
<gadget id="calculator">9 - 1</gadget>
<output>8</output>

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">9 * 4</gadget>
<output>36</output>

<result>36</result>