Decades have passed since the beginning of AtCoder Beginner Contest.
The contests are labeled as ABC001, ABC002, ... from the first round, but after the 999-th round ABC999, a problem occurred: how the future rounds should be labeled?
In the end, the labels for the rounds from the 1000-th to the 1998-th are decided: ABD001, ABD002, ..., ABD999.
You are given an integer N between 1 and 1998 (inclusive). Print the first three characters of the label of the N-th round of AtCoder Beginner Contest.

-----Constraints-----
 - 1 \leq N \leq 1998
 - N is an integer.

-----Input-----
Input is given from Standard Input in the following format:
N

-----Output-----
Print the first three characters of the label of the N-th round of AtCoder Beginner Contest.

-----Sample Input-----
999

-----Sample Output-----
ABC

The 999-th round of AtCoder Beginner Contest is labeled as ABC999.

Difficulty: EASY

Solutions:
print('ABC') if int(input()) <= 999 else print('ABD')


N = int(input())
print('ABC') if N < 1000 else print('ABD')


print('AB' + 'CD'[int(input()) > 999])


n = int(input())
print('ABC' if n < 1000 else 'ABD')


N = int(input())
print('AB' + ['C', 'D'][N >= 1000])


n = int(input())
print('ABC' if len(str(n)) <= 3 else 'ABD')


print(['ABC', 'ABD'][int(input()) > 999])


print('AABBCD'[int(input()) > 999::2])


print(('ABC', 'ABD')[int(input()) >= 1000])


s = int(input())
if s >= 1000:
	print('ABD')
else:
	print('ABC')


ans = 'ABC' if int(input()) < 1000 else 'ABD'
print(ans)


print('ABC' if int(input().strip()) < 1000 else 'ABD')


a = 'ABD'
if int(input()) < 1000:
	a = 'ABC'
print(a)


X = int(input())
if X < 1000:
	print('ABC')
else:
	print('ABD')


print('AB' + ('C', 'D')[int(input()) > 999])


N = int(input())
if N < 1000:
	print('ABC')
elif N >= 1000:
	print('ABD')


def main():
	n = int(input())
	print('ABC' if n < 1000 else 'ABD')
main()


n = int(input())
if len(str(n)) == 4:
	print('ABD')
else:
	print('ABC')


n = int(input())
print('AB' + ('C' * (n <= 999) or 'D'))


N = int(input())
print('AB' + chr(67 + (N > 999)))


print('AABBDC'[int(input()) < 1000::2])


n = int(input())
print('AB' + 'C' * (n < 1000) + 'D' * (n >= 1000))


print('AB' + ('C' if int(input()) < 1000 else 'D'))


n = int(input())
if n <= 999:
	c = 'ABC'
else:
	c = 'ABD'
print(c)


n = int(input())
x = n - 999 if n > 999 else n
if n > 999:
	print('ABD')
else:
	print('ABC')


contest_N = int(input())
if contest_N >= 1000:
	print('ABD')
else:
	print('ABC')


N = int(input())
if N <= 999:
	print('ABC')
elif N > 999:
	print('ABD')


i = int(input())
if i < 1000:
	print('ABC')
else:
	print('ABD')


A = int(input())
print('ABC' if A < 1000 else 'ABD')


N = int(input().strip())
print('AB' + 'C D'.split()[N >= 1000])


n = int(input())
if n <= 999:
	ans = 'ABC'
else:
	ans = 'ABD'
print(ans)


N = int(input())
ans = 'ABD' if N > 999 else 'ABC'
print(ans)


print('AB' + 'DC'[int(input()) < 1000])


import sys
import math
sys.setrecursionlimit(10 ** 8)
ini = lambda : int(sys.stdin.readline())
inm = lambda : map(int, sys.stdin.readline().split())
inl = lambda : list(inm())
ins = lambda : sys.stdin.readline().rstrip()
debug = lambda *a, **kw: print('\x1b[33m', *a, '\x1b[0m', **dict(file=sys.stderr, **kw))
N = ini()
if N <= 999:
	print('ABC')
else:
	print('ABD')


ans = 'ABC'
if int(input()) > 999:
	ans = 'ABD'
print(ans)