题解 | #牛牛的绩点#

# 总感觉写复杂了
dict1 = {'A':4.0, 'B':3.0, 'C':2.0, 'D':1.0, 'F':0}
list1 = []
sum = 0
score = 0
while True:
    t = input()
    if t == 'False':
        break
    list1.append(t)
for i in range(len(list1)):
    if i%2 ==1:
        continue
    sum += dict1[list1[i]] * int(list1[i+1])
    score += int(list1[i+1])
print('%.2f' % (sum/score))