题解 | #牛牛的绩点#

dict1 = {'A':4.0,'B':3.0,'C':2.0,'D':1.0,'F':0}
list1 = []
list2 = []
while True:
    first_ele = input('')
    if first_ele == 'False':
        break
    else:
        second_ele = int(input())
        list1.append(dict1[first_ele]*second_ele)
        list2.append(second_ele)
print('%.2f'%(sum(list1)/sum(list2)))