The Yangshan Education System held a men's basketball game. There were 5 teams in the center group participating in the game. Now there is a game between every two teams. How many games will the center group have in total?
阳山教育系统举行男子篮球比赛，中心组共有5个队参加比赛，现每两个队之间都要进行一场比赛，中心组一共要进行多少场比赛．
<gadget id="calculator">5 - 1</gadget>
<output>4</output>

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

<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<result>10</result>