New Sunshine School is about to hold a sports meeting. A total of 12 athletes in the sixth grade signed up for the 50-meter sprint competition. Ask the students to calculate, if every two people shake hands once, how many times they shook hands in total.
新阳光学校即将举行体育运动会，六年级报名参加50米短跑比赛的一共有12名运动员．请同学们算一算，如果每两人握一次手，一共握了多少次手．
<gadget id="calculator">12 - 1</gadget>
<output>11</output>

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">11 * 6</gadget>
<output>66</output>

<result>66</result>