The teacher needs to send an emergency notice to the whole class in the shortest possible time. Assuming a phone call, it takes 1 minute to notify each classmate. The teacher notifies classmate A in the first minute, and classmate A notifies classmate B in the second minute. At the same time, the teacher notifies classmate C, and so on. If there is no repetition, a total of 5 minutes How many students can be notified?
老师有急事需要在最短的时间内向全班同学发紧急通知．假定用电话联系，每通知一个同学需要1分钟，第1分钟由老师通知同学A，第2分钟由同学A通知同学B，同时老师通知同学C，依此类推，如果没有重复，5分钟内共可以通知多少名同学？
<gadget id="calculator">2 ** 5</gadget>
<output>32</output>

<gadget id="calculator">32 - 1</gadget>
<output>31</output>

<result>31</result>