def checkMark(x):
    if 80<=x<=100:
        print("4.00")
    elif 75<=x<=89:
        print("3.75")
    elif 70 <= x <= 74:
        print("3.50")
    elif 65 <= x <= 69:
        print("3.25")
    elif 60 <= x <= 64:
        print("3.00")
    elif 55 <= x <= 59:
        print("2.75")
    elif 50 <= x <= 54:
        print("2.50")
    elif 45 <= x <= 49:
        print("2.25")
    elif 40 <= x <= 44:
        print("2.00")
    elif 0<= x <= 39:
       print("Fail")

a=float (input("Enter your mark : "))
print(checkMark(a))