Two classes have a badminton match, each class selects 4 players, each player has to play one game against each player of the other side, how many games will be played in total.
两个班进行羽毛球比赛，每班选4人，每人都要和对方的每个选手赛一场，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>