The school must notify the students of urgent matters, and requires telephone contact, and it takes 1 minute to notify a classmate. In the first minute, the teacher informs student A, in the second minute, the teacher informs student B, and at the same time, student A informs student C, in the third minute..., and so on, how many students are notified in total in 6 minutes.
学校有急事必须通知学生，要求用电话联系，每通知一个同学要用1分钟．第一分钟是老师通知A同学，第二分钟是老师通知B同学，同时A同学通知C同学，第三分钟…，以此类推，在6分钟里一共通知了多少位同学．
<gadget id="calculator">2 ** 6</gadget>
<output>64</output>

<gadget id="calculator">64 - 1</gadget>
<output>63</output>

<result>63</result>