题解 | 牛牛的绩点

import sys

d = {'A': 4, 'B': 3, 'C': 2, 'D': 1, 'F': 0}
s = input()
num1 = 0
num2 = 0
while s != "False":
    s1 = int(input())
    num1 += d[s] * s1
    num2 += s1
    s = input()
print("%.2f"%(num1 / num2))