grade ={
    "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
}
line = [input().split() for _ in range(20)]
credit = sum(float(line[i][1]) for i in range(20) if line[i][2] != 'P')
rate = sum(float(line[i][1])*grade[line[i][2]] for i in range(20) if line[i][2] != 'P')
print(round(rate/credit,6))