There are 15 students in the mathematics group of Class 61. Teacher Gao has an urgent matter to inform everyone on weekends. It takes 1 minute for each person to be notified. If the most reasonable method is adopted, how many minutes is the minimum required to inform all the students.
六一班数学小组有15位同学，周末高老师有一急事需要通知大家，每通知一人需要1分钟．如果采用最合理的方法，通知完全部同学最少需多少分钟．
<result>4</result>