# 시험 성적 9498

a = int(input())

if a >= 90 and a <= 100:

print("A")

elif a <= 89 and a >= 80:

print("B")

elif a <= 79 and a >= 70:

print("C")

elif a <= 69 and a >= 60:

print("D")

else:

print("F")

# 주사위 세 개 2480

a, b, c = map(int, input().split())

answer = 0

if a == b == c:

answer = 10000 + a * 1000

elif a != b and a != c and b != c:

answer = max([a, b, c]) * 100

else:

if a == b or a == c:

answer = 100 * a + 1000

else:

answer = 100 * b + 1000

print(answer)

# 바구니 뒤집기 10811

n, m = map(int, input().split())

seq = [i for i in range(n+1)]

for p in range(m):

i, j = map(int, input().split())

for q in range((j - i + 1) // 2):

seq[i + q], seq[j - q] = seq[j - q], seq[i + q]

print(*seq[1:])

# 소수 찾기 1978

import math

n = int(input())

lst = list(map(int, input().split()))

def is_prime_num(n):

if n == 1:

return 0

for i in range(2, int(math.sqrt(n)) + 1):

if not n % i:

return 0

return 1

count = 0

for i in lst:

if is_prime_num(i):

count += 1

print(count)

# 설탕 배달 2839

n = int(input())

answer = 0

while True:

if not n % 5:

answer += n // 5

break

n -= 3

answer += 1

if n > 0 and n < 3:

answer = -1

break

print(answer)

# 11651 좌표 정렬하기 2

n = int(input())

lst = []

for i in range(n):

x, y = map(int, input().split())

lst.append((x, y))

lst.sort(key = lambda x : (x[1], x[0]))

for i in range(n):

print(*lst[i])

# 1181 단어 정렬

n = int(input())

lst = set()

for i in range(n):

lst.add(input().rstrip())

lst = list(lst)

lst.sort()

lst.sort(key = len)

for i in lst:

print(i)

# 10815 숫자 카드

n = int(input())

lst = set(map(int, input().split()))

m = int(input())

for i in map(int, input().split()):

print(1 if i in lst else 0, end = ' ')

# 1764 듣보잡

n, m = map(int, input().split())

a = set()

b = set()

for i in range(n):

a.add(input().rstrip())

for i in range(m):

b.add(input().rstrip())

c = a & b

c = list(c)

c.sort()

print(len(c))

for i in c:

print(i)