题解 | #牛牛的绩点#

pf = {
    'A':4.0,
    'B':3.0,
    'C':2.0,
    'D':1.0,
    'F':0,
}
dic = {}
while True:
    t = input()
    if t != 'False':
        if t in dic.keys():
            dic[t]=dic[t] + float(input())
        else:
            dic[t]= float(input())
    else:
        break
# print(list(dic.values()))
sum_scores=sum(list(dic.values()))
sum_scores_with_quan = 0.0
for i in list(dic.keys()):
    sum_scores_with_quan = sum_scores_with_quan + dic[i] * pf[i]
print("%.2f" % (sum_scores_with_quan / sum_scores))