score = {'A':4.0, 'B':3.0, 'C':2.0, 'D':1.0, 'F':0}
niu_score = {}
score_sum = 0
credit_sum = 0

flag = str(input())
while flag != 'False':
    assert flag in score.keys()
    credit = float(input())
    score_sum += credit * score[flag]
    credit_sum += credit
    flag = str(input())

    

print(f'{score_sum / credit_sum:.2f}')