num = int(input())
if num>=140:
    print("A")
if num <= 139 and num >=120:
    print("B")
if num <= 119 and num >=110:
    print("C")
if num <= 109 and num >=90:
    print("D")
if num <= 89 and num >=80:
    print("E")
if num <= 79 and num >=70:
    print("F")
if num <= 69:
    print("G")