The senior students of Nanmo Elementary School organized a friendly chess match. A total of 6 students participated in the game. According to the rules of the game, every two students have to play a game. So, how many games will they have in total?
南莫小学高年级同学组织了一场象棋友谊赛，共有6名同学参加了比赛，根据比赛规则，每两名同学之间都要进行一场比赛，那么，他们一共要赛多少场．
<gadget id="calculator">6 - 1</gadget>
<output>5</output>

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

<gadget id="calculator">5 * 3</gadget>
<output>15</output>

<result>15</result>