There are four teams from China, Canada, Australia, and Russia. Every two teams have to play a game. How many games are there in total?
中国、加拿大、澳大利亚、俄罗斯四支球队，每2支球队之间都要进行一场比赛，共要比赛多少场．
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">3 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">4 * (3/2)</gadget>
<output>6</output>

<result>6</result>