题解 | #牛牛的绩点#

import sys


List = []
for i in sys.stdin:
    if "False" not in str(i):
        List.append(i)

junji = 0
score = 0
for i in range(len(List)):
    if "A" in List[i]:
        junji += int(List[i+1]) * 4
        score += int(List[i+1])
    elif "B" in List[i]:
        junji += int(List[i+1]) * 3
        score += int(List[i+1])
    elif "C" in List[i]:
        junji += int(List[i+1]) * 2
        score += int(List[i+1])
    elif "D" in List[i]:
        junji += int(List[i+1]) * 1
        score += int(List[i+1])
    elif "F" in List[i]:
        junji += 0
        score += int(List[i+1])
print("%.2f" % (junji / score))