题解 | #牛牛的绩点#

dict1 = {'A': 4.0, 'B': 3.0, 'C': 2.0, 'D': 1.0, 'F': 0}
list1 = [] # 等级 * 学分 = 总成绩
list2 = [] # 学分数
while True:
    grade = input()
    if grade == 'False':
        break
    else:
        score = int(input())
        list1.append(dict1[grade] * score)
        list2.append(score)
print('{:.2f}'.format(sum(list1) / sum(list2)))