n = int(input())

if n >= 90:
    print("A")
elif n >= 80:
    print("B")
elif n >= 70:
    print("C")
else:
    print("F")

num = [1, 3, 4, 5, 6]

num.append(7)
print(num)

num.insert(1, 2)
print(num)

num.remove(1)
print(num)

num2 = [3, 6, 7, 2, 4, 1, 5]
num2.sort()
print(num2)