题解 | #牛牛的绩点#

import sys


#学分和绩点的乘积求和，除以学分的求和
performance={"A":4.0,"B":3.0,"C":2.0,"D":1.0,"F":0.0}
credit=[]
multis=[]
while True:
    grade=input()
    if grade=='False':
        break
    # 学分credit
    num=int(input())
    credit.append(num)
    multis.append(num*performance[grade])
print('{:.2f}'.format(sum(multis)/sum(credit)))
    


for line in sys.stdin:
    a = line.split()
    print(int(a[0]) + int(a[1]))