'''print('hello world!')
a = 10
print(a)
b = 10.2
print(b-a)
c = [3, 5, 8, 10]
print(c[1])
print(c[1:4])
c.append(13)
print(c)
c.insert(2, 6)
print(c)
c.remove(3)
print(c)

d = input()
print(d)

a = int(input())
print(a * 10)
b = int(input())
print(a + b)
print(a - b)
print(a * b)
print(a / b)

c = int(input())
if c >= 10:
    print(1)
else:
    print(0)
'''

score = int(input())
if score >= 90:
    print('A')
elif score >= 80:
    print('B')
elif score >= 70:
    print('C')
else:
    print('F')

age = int(input())
if age >= 8 and age <= 13:
    print('초등학생')