4 players A, B, C, and D play a game of checkers, and every 2 players play one game. How many games will there be in total?
甲、乙、丙、丁4个人进行跳棋比赛，每2个人赛一场，一共要赛多少场．
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

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

<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<result>6</result>