题解 | #牛牛的绩点#

dic={'A':4.0,'B':3.0,'C':2.0,'D':1.0,'F':0}
sum1=0
tmp=0
while True:
    grade=input()
    if grade=='False':
        break
    else:
        scores=int(input())
        sum1+=dic[grade]*scores
        tmp+=scores
ave=format((sum1/tmp),'.2f')
print(ave)