题解 | #牛牛的绩点#

import sys


a = []
total = 0.00
mark = 0
b = input()
while b != "False":
    a = input()
    a = int(a)
    mark += a
    if b == "A":
        total += 4.0 * a
    elif b == "B":
        total += 3.0 * a
    elif b == "C":
        total += 2.0 * a
    elif b == "D":
        total += 1.0 * a
    elif b == "F":
        total += 0.0 * a
    b = input()
print("{:.2f}".format(total/mark))