One day the teacher found out that among the 50 students in the class, some students did not wear the red scarf, and one of any two students must wear the red scarf, so how many people did not wear the red scarf?
一天老师发现全班50个学生中有学生没戴红领巾，并且任何两个学生中必有一个戴了红领巾，那么共有多少人没戴红领巾？
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