There are 18 people in a football team, and there is an urgent game task, the coach needs to notify each team member as soon as possible. If you use the phone call, notify one person per minute, and each team member will notify others immediately after receiving the notification. How long does it take at least to notify all team members?
一个足球队有18人，有一个紧急比赛任务，教练需要尽快通知到每一个队员．如果用打电话的方式，每分钟通知1人，每个队员接到通知后马上通知别人．最少花多长的时问就能通知到全体队员？
<result>5</result>