There are 6 football teams, and there is at most one game between each two teams. If each team has played exactly 2 games, how many match arrangements are eligible?
6支足球队，每两队间至多比赛一场如果每队恰好比赛了2场，那么符合条件的比赛安排共有多少种．
<gadget id="calculator">6 * 5 * 4</gadget>
<output>120</output>

<gadget id="calculator">3 * 2 * 1</gadget>
<output>6</output>

<gadget id="calculator">120 / 6 / 2</gadget>
<output>10</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">5 * 4 * 3 * 2 * (1/2)</gadget>
<output>60</output>

<gadget id="calculator">10 + 60</gadget>
<output>70</output>

<result>70</result>