题解 | #牛牛的绩点#
牛牛的绩点
https://www.nowcoder.com/practice/de8bc3e736164786b07a4dd64ed172f7
a={'A':4,'B':3,'C':2,'D':1,'F':0}
x=input()
sum=0
count=0
while x!='False':
b=int(input())
sum+=a[x]*b
count+=b
x=input()
average=sum/count
print('%.2f'%(average))
