题解 | #牛牛的绩点#

n = 0.00
t = 0
while True:
    grade = input()
    if grade == 'False':
        break
    
    score = 0.0
    point = int(input())

    if grade == 'A':
        score = 4.0
    elif grade == 'B':
        score = 3.0
    elif grade == 'C':
        score = 2.0
    elif grade == 'D':
        score = 1.0
    else:
        score = 0.0
    
    n = n + point * score
    t = t + point
r = n/t
print(f'%.2f' %r)