score_dict = {"A+":4.5, "A0":4.0, "B+":3.5, "B0":3.0, "C+":2.5, "C0":2.0, "D+": 1.5, "D0": 1.0, "F":0.0}
total_score = 0
total_credit = 0
for _ in range(20):
    _, credit, score = input().split()
    if score == "P":
        continue
    total_score += float(credit) * score_dict[score]
    total_credit += float(credit)
print(total_score/total_credit)