8 people are playing a chess game, each of them will play 1 game, how many games will be played in total.
8个人进行象棋赛，每两人都要赛1盘，一共需要赛多少盘．
<gadget id="calculator">8 - 1</gadget>
<output>7</output>

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

<gadget id="calculator">7 * 4</gadget>
<output>28</output>

<result>28</result>