Problem Q: 成绩考核

Problem Q: 成绩考核

Time Limit: 1 Sec  Memory Limit: 128 MB
Submit: 2378  Solved: 1022
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Description

学生期末考试3门课的平均成绩大于或者等于90, 则为等级A
大于等于70, 则为等级B
大于等于50, 则为等级C
小于50, 等级F

Input

92 93.5 91

Output

A

Sample Input

90 90.1 90.2

Sample Output

A

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