Problem:
 Score : 100 points    Problem Statement 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 1 999      Sample Output 1 ABC  The 999 -th round of AtCoder Beginner Contest is labeled as ABC999 .       Sample Input 2 1000      Sample Output 2 ABD  The 1000 -th round of AtCoder Beginner Contest is labeled as ABD001 .       Sample Input 3 1481      Sample Output 3 ABD  The 1481 -th round of AtCoder Beginner Contest is labeled as ABD482 .

Solution (Python):
from collections import defaultdict
import sys,heapq,bisect,math,itertools,string,queue,datetime
sys.setrecursionlimit(10**8)
INF = float('inf')
mod = 10**9+7
eps = 10**-7
def inpl(): return list(map(int, input().split()))
def inpl_str(): return list(input().split())

N = int(input())

if N >= 1000:
    print('ABD')
else:
    print('ABC')

Solution (Python):
n = int(input())
if n <= 999:
  print("ABC")
else:
  print("ABD")

Solution (Python):
import sys, os

f = lambda:list(map(int,input().split()))
if 'local' in os.environ :
    sys.stdin = open('./input.txt', 'r')

def solve():
    n = f()[0]
    if n>=1000:
        print('ABD')
    else:
        print('ABC')

solve()

Solution (Python):


import sys


s2nn = lambda s: [int(c) for c in s.split(' ')]
ss2nn = lambda ss: [int(s) for s in ss]
ss2nnn = lambda ss: [s2nn(s) for s in ss]
i2s = lambda: sys.stdin.readline().rstrip()
i2n = lambda: int(i2s())
i2nn = lambda: s2nn(i2s())
ii2ss = lambda n: [sys.stdin.readline().rstrip() for _ in range(n)]
ii2nn = lambda n: ss2nn(ii2ss(n))
ii2nnn = lambda n: ss2nnn(ii2ss(n))

def main():
    N = i2n()
    if N <= 999:
        print('ABC')
    else:
        print('ABD')

main()

Solution (Python):
N = int(input())

if N > 999:
    print ('ABD')
else:
    print ('ABC')

Solution (Python):
N = int(input())

if N <= 999:
    print('ABC')
else:
    print('ABD')

Solution (Python):

import sys


def solve(N: int):
    if N < 1000:
        ret = 'ABC'
    else:
        ret = 'ABD'
    print(ret)
    return


def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    N = int(next(tokens))  
    solve(N)

if __name__ == '__main__':
    main()

Solution (Python):
n = int(input())
if n >= 1000:
  print("ABD")
else:
  print("ABC")

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

Solution (Python):
print("ABC" if len(input())<=3 else "ABD")

Solution (Python):


from sys import stdout
from bisect import bisect_left as binl
from copy import copy, deepcopy
from collections import defaultdict


mod = 1


def intin():
    input_tuple = input().split()
    if len(input_tuple) <= 1:
        return int(input_tuple[0])
    return tuple(map(int, input_tuple))


def intina():
    return [int(i) for i in input().split()]


def intinl(count):
    return [intin() for _ in range(count)]


def modadd(x, y):
    global mod
    return (x + y) % mod


def modmlt(x, y):
    global mod
    return (x * y) % mod


def lcm(x, y):
    while y != 0:
        z = x % y
        x = y
        y = z
    return x


def combination(x, y):
    assert(x >= y)

    if y > x // 2:
        y = x - y

    ret = 1

    for i in range(0, y):
        j = x - i
        i = i + 1

        ret = ret * j
        ret = ret // i

    return ret


def get_divisors(x):
    retlist = []
    for i in range(1, int(x**0.5) + 3):
        if x % i == 0:
            retlist.append(i)
            retlist.append(x // i)
    return retlist


def get_factors(x):
    retlist = []
    for i in range(2, int(x**0.5) + 3):
        while x % i == 0:
            retlist.append(i)
            x = x // i
    retlist.append(x)
    return retlist


def make_linklist(xylist):
    linklist = {}
    for a, b in xylist:
        linklist.setdefault(a, [])
        linklist.setdefault(b, [])
        linklist[a].append(b)
        linklist[b].append(a)
    return linklist


def calc_longest_distance(linklist, v=1):
    distance_list = {}
    distance_count = 0
    distance = 0
    vlist_previous = []
    vlist = [v]
    nodecount = len(linklist)

    while distance_count < nodecount:
        vlist_next = []
        for v in vlist:
            distance_list[v] = distance
            distance_count += 1
            vlist_next.extend(linklist[v])
        distance += 1
        vlist_to_del = vlist_previous
        vlist_previous = vlist
        vlist = list(set(vlist_next) - set(vlist_to_del))

    max_distance = -1
    max_v = None
    for v, distance in distance_list.items():
        if distance > max_distance:
            max_distance = distance
            max_v = v

    return (max_distance, max_v)


def calc_tree_diameter(linklist, v=1):
    _, u = calc_longest_distance(linklist, v)
    distance, _ = calc_longest_distance(linklist, u)
    return distance





def main():
    n = intin()

    if n < 1000:
        print('ABC')
    else:
        print('ABD')


if __name__ == '__main__':
    main()

Solution (Python):

N = int(input())

if N <= 999:
    print('ABC')
else:
    print('ABD')

Solution (Python):
N = int(input())
if N <= 999:
    print("ABC")
else:
    print("ABD")

Solution (Python):
N = int(input())
under = "ABC"
over = "ABD"

if N > 1000:

  print(over)
elif N == 1000:
  print("ABD")
else:

  print(under)

Solution (Python):
N = int(input())
print("ABC" if N < 1000 else "ABD")

Solution (Python):
import sys
input = sys.stdin.readline

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

Solution (Python):
s = input()
print("ABD") if len(s) > 3 else print("ABC")

Solution (Python):
N=int(input())
if N>=1000:
    print("ABD")
elif N<1000:
    print("ABC")

Solution (Python):
n=int(input())
if n<=999:
    print("ABC")
else:
    print("ABD")

Solution (Python):
N = int(input())

if N <= 999:
    print("ABC")
else:
    print("ABD")

Solution (Python):
N = int(input())

if N <= 999:
    print("ABC")
else:
    print("ABD")

Solution (Python):
n = int(input())
if n < 1000:
    print("ABC")
else:
    print("ABD")

Solution (Python):
a = int(input())
if(a < 1000):
  print("ABC")
else:
  print("ABD")

Solution (Python):
n = int(input())
if n<1000:
    print("ABC")
else:
    print("ABD")

Solution (Python):
N=int(input())
if N<1000:
    print("ABC")
else:
    print("ABD")

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

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

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

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

Solution (Python):
import sys


def input():
    return sys.stdin.readline()[:-1]






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

Solution (Python):


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


if __name__ == '__main__':
    main()

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

Solution (Python):
input_data = int(input())
if input_data <= 999:
    print('ABC')
else:
    print('ABD')

Solution (Python):


 

n = int(input())


if n < 1000:
  ans = "ABC"
else:
  ans = "ABD"


print(ans)

Solution (Python):
N = int(input())

if N <= 999:
    print('ABC')
else:
    print('ABD')

Solution (Python):
n = int(input())
if n<1000:
    print("ABC")
else:
    print("ABD")

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

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

Solution (Python):
n = int(input())
if n >= 1000:
    print("ABD")
else:
    print("ABC")

Solution (Python):
def main():
    N = int(input())
    if N < 1000:
        print("ABC")
    else:
        print("ABD")
    

if __name__=='__main__':
    main()

Solution (Python):
n = int(input())

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

Solution (Python):
n=int(input())

if n<=999:
    print("ABC")
else:
    print("ABD")

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

Solution (Python):
n=int(input())

if n<1000:
  print("ABC")
else:
  print("ABD")

Solution (Python):
N = int(input())
print('AB' + chr(N // 1000 + 67))

Solution (Python):
N = int(input())
if N <= 999:
  print("ABC")
else:
  print("ABD")

Solution (Python):
print("ABC" if int(input()) < 1000 else "ABD")

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

Solution (Python):
a = input()
if int(a) <= 999:
  print("ABC")
else:
  print("ABD")

Solution (Python):


def read_input():
    n = int(input())
    return n


def submit():
    n = read_input()

    if n < 1000:
        print('ABC')
    else:
        print('ABD')

if __name__ == '__main__':
    submit()

Solution (Python):
n = int(input())

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

Solution (Python):
N = int(input())

if N >=1000:
    print('ABD')
else:
    print('ABC')

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

Solution (Python):
n = int(input())
if n < 1000:
  print("ABC")
else:
  print("ABD")

Solution (Python):
a=int(input())

if a>= 1000:
 print("ABD")
else:
 print("ABC")

Solution (Python):
print("AB"+["D","C"][int(input())<1000])

Solution (Python):
if int(input()) < 1000:
    print('ABC')
else:
    print('ABD')

Solution (Python):
a = int(input())
if a <= 999:
    print('ABC')
else:
    print('ABD')

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

Solution (Python):
x = int(input())

if x < 1000:
  print("ABC")
else:
  print("ABD")

Solution (Python):

import numpy as np
import math
import re
import functools

n = int(input())

if(n > 999):
    print('ABD')
else:
    print('ABC')

Solution (Python):
from collections import Counter
from functools import reduce

import bisect
import copy
import fractions
import math
import random
import sys
import time
sys.setrecursionlimit(10**7)
INF = 10 ** 18
MOD = 10 ** 9 + 7
def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def MI(): return map(int, sys.stdin.readline().split())
def II(): return int(sys.stdin.readline())
def IS(): return input()
def C(x): return Counter(x)
def GCD_LIST(numbers):
    return reduce(fractions.gcd, numbers)
def LCM_LIST(numbers):
    return reduce(LCM, numbers)
def LCM(m, n):
    return (m * n // fractions.gcd(m, n))

def unite(x, y):
    
    x = root(x)
    y = root(y)
    if x == y:
        return
    
    node[x] = y
def same(x,y): return bool(root(x) == root(y))
def root(x):
    if node[x] == x:  
        return x
    else:
        node[x] = root(node[x])  
        return node[x]

print('ABC') if II() <= 999 else print('ABD')

Solution (Python):
n = int(input())
 
if n<= 999:
    print("ABC")
else:
    print("ABD")

Solution (Python):
n = int(input())

if n<= 999:
    print("ABC")
else:
    print("ABD")

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

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

Solution (Python):
n = int(input())
print("ABC" if n < 1000 else "ABD")

Solution (Python):



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

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

Solution (Python):

import numpy as np
import math
import re
import functools

n = int(input())

if(n > 999):
    print('ABD')
else:
    print('ABC')

Solution (Python):
N=int(input())
if N>999:
    print("ABD")
else:
    print("ABC")

Solution (Python):
N = int(input())
if N<=999:
	print('ABC')
else:
	print('ABD')

Solution (Python):
N = int(input())
if N<=999:
    print('ABC')
else:
    print('ABD')

Solution (Python):
N = input()
if len(N)>3:
    print("ABD")
else:
    print("ABC")

Solution (Python):
n = int(input())
if n <= 999:
    print("ABC")
else:
    print("ABD")

Solution (Python):
import sys
input = sys.stdin.readline

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

Solution (Python):
a=int(input())
if a<=999:
  print("ABC")
else:
  print("ABD")

Solution (Python):
n=int(input())
if n<=999:
    print("ABC")
else:
    print("ABD")

Solution (Python):
N = int(input())
if N < 1000:
    print("ABC")
else:
    print("ABD")

Solution (Python):
print("ABC" if int(input())<1000 else "ABD")

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

Solution (Python):
N = int(input())

if N <= 999:
    print('ABC')
else:
    print('ABD')

Solution (Python):
print("ABC" if int(input())<=999 else "ABD")

Solution (Python):
a=input()
print(["ABC","ABD"][len(a) > 3])

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

Solution (Python):
n=int(input())
a=n%1000
if n<1000:
  print("ABC")
else:
  print("ABD")

Solution (Python):
print("ABC" if int(input())<1000 else "ABD")

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

Solution (Python):
import sys
import numpy as np

readInt = lambda: int(sys.stdin.readline())
readIntN = lambda: [int(v) for v in sys.stdin.readline().split(' ')]

n = readInt()
ret = 'AB' + ('C' if n < 1000 else 'D')
print(ret)

Solution (Python):
import functools

import os

INF = float('inf')


def inp():
    return int(input())


def inpf():
    return float(input())


def inps():
    return input()


def inl():
    return list(map(int, input().split()))


def inlf():
    return list(map(float, input().split()))


def inls():
    return input().split()


def debug(fn):
    if not os.getenv('LOCAL'):
        return fn

    @functools.wraps(fn)
    def wrapper(*args, **kwargs):
        print('DEBUG: {}({}) -> '.format(
            fn.__name__,
            ', '.join(
                list(map(str, args)) +
                ['{}={}'.format(k, str(v)) for k, v in kwargs.items()]
            )
        ), end='')
        ret = fn(*args, **kwargs)
        print(ret)
        return ret

    return wrapper

a = inp()
if a >= 1000:
    print('ABD')
else:
    print('ABC')

Solution (Python):
N = int(input())
if N <= 999:
    print('ABC')
else:
    print('ABD')

Solution (Python):
n=int(input())

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

Solution (Python):
N = int(input())
if N<1000:
  print("ABC")
else:
  print("ABD")

Solution (Python):

print("ABC" if int(input()) <= 999 else "ABD")

Solution (Python):
def main():
	N = int(input())
	if N < 1000:
		print("ABC")
	else:
		print("ABD")

if __name__ == '__main__':
    main()

Solution (Python):
N = int(input())
if(N<1000):
    print("ABC")
else:
    print("ABD")

Solution (Python):
print("ABC" if int(input())<=999 else "ABD")

Solution (Python):
N = int(input())

if N < 1000:
    print('ABC')
else:
    print('ABD')

Solution (Python):
if int(input()) < 1000:
	print("ABC")
else:
	print("ABD")

Solution (Python):
n = int(input())
if n < 1000:
    print("ABC")
else:
    print("ABD")

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

Solution (Python):

import sys
INF = float("inf")


def solve(N: int):
    if N <= 999:
        print("ABC")
    else:
        print("ABD")

    return


def main():

    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    N = int(next(tokens))  
    solve(N)


if __name__ == '__main__':
    main()

Solution (Python):
N=int(input())
if N<=999:
 print('ABC')
else:
 print('ABD')

Solution (Python):
N = int(input())
print('ABD') if N >= 1000 else print('ABC')

Solution (Python):
num = input()
num = int(num)
if num < 1000:
  print('ABC')
else:
  print('ABD')

Solution (Python):
N = int(input())
if N < 1000:
    print("ABC")
else:
    print("ABD")

Solution (Python):


n = input()

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

Solution (Python):
print("ABC" if int(input())<=999 else "ABD")

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

Solution (Python):
n = int(input())

print('ABC') if n<= 999 else print('ABD')

Solution (Python):
N = int(input())

if N  <= 999:
    print("ABC")
else:
    print("ABD")

Solution (Python):
print('ABC' if int(input()) < 1000 else 'ABD')

Solution (Python):
n=int(input())
if(n<1000):
    print("ABC")
else:
    print("ABD")

Solution (Python):
print("ABD" if len(input()) > 3 else "ABC")

Solution (Python):
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians
from itertools import permutations, combinations, product
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
MOD = 10 ** 9 + 7

N = input()
if 1 <= int(N) <= 999:
	print("ABC")
else:
	print("ABD")

Solution (Python):
import sys
import re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians
from itertools import permutations, combinations, product
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits


def input(): return sys.stdin.readline().strip()


def INT(): return int(input())


def MAP(): return map(int, input().split())


def LIST(): return list(map(int, input().split()))


sys.setrecursionlimit(10 ** 9)
INF = float('inf')
MOD = 10 ** 9 + 7

n = INT()

if n < 1000:
    print('ABC')
else:
    print('ABD')

Solution (Python):
a = int(input())
if a >= 1 and a <= 999 :
    print('ABC')
elif a >= 1000 :
    print('ABD')

Solution (Python):
N = int(input())

if N < 1000:
    print('ABC')
else:
    print('ABD')

Solution (Python):
N = int(input())

if N < 1000:
    print('ABC')
else:
    print('ABD')

Solution (Python):
if 1000 <= int(input()):
    print("ABD")
else:
    print("ABC")

Solution (Python):

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

Solution (Python):
N = int(input())

if(N <= 999):
  print('ABC')

if(N > 999):
  print('ABD')

Solution (Python):
n=int(input())
if n>=1000:
  print('ABD')
else:
  print('ABC')

Solution (Python):
N = int(input())
print("ABC" if N<=999 else "ABD")

Solution (Python):
a=int(input())
if a<=999:
    print("ABC")
else:
    print("ABD")

Solution (Python):
N = int(input())

if N-1000 < 0:
  print('ABC')
else:
  print('ABD')

Solution (Python):
N = int(input())
if N <= 999:
    print('ABC')
else:
    print('ABD')

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

Solution (Python):
N = int(input())
if(N <1000):
  ans = 'ABC' 
else:
  ans = 'ABD'
print(ans)

Solution (Python):
n=int(input())
if 0<n<1000:
	print("ABC")
else:
	print("ABD")

Solution (Python):
N= int(input())
print("ABC" if N<1000 else "ABD")

Solution (Python):
print('ABC' if int(input()) < 1000 else 'ABD')

Solution (Python):
N = int(input())
if N <= 999:
    print("ABC")
else:
    print("ABD")

Solution (Python):
n=int(input())
print("ABC" if n<1000 else "ABD")

Solution (Python):
print('ABC' if int(input()) < 1000 else 'ABD')

Solution (Python):


def main():
    N = int(input())
    print("ABC") if N < 1000 else print("ABD")
    
    

if __name__ == '__main__':
    main()

Solution (Python):
N = str(input())
if int(N) >= 1 and int(N) <= 999:
    print("ABC")
elif int(N) >= 1000 and int(N) <= 1998:
    print("ABD")

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

Solution (Python):
print(["ABC", "ABD"][not(int(input())<1000)])

Solution (Python):
n = int(input())
if n <= 999:
  print("ABC")
else:
  print("ABD")

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

Solution (Python):
a=int(input())
if a<=999:
  print("ABC")
else:
  print("ABD")

Solution (Python):
print("AB"+"CD"[len(input())>3])

Solution (Python):
N = int(input())

if N <= 999:
    print('ABC')
else:
    print('ABD')

Solution (Python):
n = int(input())

print("ABC" if n <= 999 else "ABD")

Solution (Python):
N = input()
N = int(N)
if N <= 999:
    print('ABC')
else:
    print('ABD')

Solution (Python):
N=int(input())
if N<1000:
    print("ABC")
else :
    print("ABD")

Solution (Python):
n=int(input())
if n<=999:
    print("ABC")
else:
    print("ABD")

Solution (Python):
N = int(input())
if N <= 999 :
    print("ABC")
else :
    print("ABD")

Solution (Python):
N = int(input())
print('ABD' if N >= 1000 else 'ABC')

Solution (Python):
n=int(input())
print("ABC" if n<1000 else "ABD")

Solution (Python):
n = input()
if n < 1000:
    print"ABC"
else:
    print"ABD"

Solution (Python):
print('ABC' if int(input()) < 1000 else 'ABD')

Solution (Python):
i=int(input())
if i>999:
  print("ABD")
else:
  print("ABC")

Solution (Python):
N = int(input())

if N>=1000:
    print("ABD")
else:
    print("ABC")

Solution (Python):
a = int(input())

if a < 1000:
    print("ABC")

else:
    print("ABD")

Solution (Python):
n = int(input())

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

Solution (Python):
a = int(input())

print("ABC" if a < 1000 else "ABD")

Solution (Python):
n = int(input())
if n>=1000:
    print('ABD')
else:
    print('ABC')

Solution (Python):
n = int(input())
print("ABC" if n < 1000 else "ABD")

Solution (Python):
s = int(input())
if s <= 999:
  print('ABC')
else:
  print('ABD')

Solution (Python):
N = int(input())
if N <= 999:
    print('ABC')
else:
    print('ABD')

Solution (Python):
print('ABC' if len(input())<4 else 'ABD')

Solution (Python):
print('AB'+'DC'[len(input())<4])

Solution (Python):
n=int(input())
print("ABC" if n<1000 else "ABD")

Solution (Python):
n=int(input())
if n<=999:
    print('ABC')
elif n<=1998:
    print('ABD')

Solution (Python):
print("ABC"if int(input())<=999 else "ABD")

Solution (Python):

from collections import defaultdict
from collections import deque
from heapq import heappush, heappop
import sys
import math
import bisect
import random
def LI(): return list(map(int, sys.stdin.readline().split()))
def I(): return int(sys.stdin.readline())
def LS():return list(map(list, sys.stdin.readline().split()))
def S(): return list(sys.stdin.readline())[:-1]
def IR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = I()
    return l
def LIR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = LI()
    return l
def SR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = S()
    return l
def LSR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = SR()
    return l
mod = 1000000007


def A():
    n = I()
    if n < 1000:
        print("ABC")
    else:
        print("ABD")
    return


def B():
    return


def C():
    n = I()
    ans = float("inf")
    for i in range(n+1):
        m = 0
        k = i
        while k > 0:
            m += k%6
            k //= 6
        k = n-i
        while k > 0:
            m += k%9
            k //= 9
        ans = min(ans,m)
    print(ans)

def D():
    n,C = LI()
    f = LIR(C)
    c = LIR(n)
    d = [defaultdict(int) for i in range(3)]
    for i in range(n):
        for j in range(n):
            d[(i+j+2)%3][c[i][j]-1] += 1
    ans = float("inf")
    for i in range(C):
        for j in range(C):
            if i != j:
                for k in range(C):
                    if k != i and k != j:
                        m = 0
                        for a in d[0].keys():
                            m += d[0][a]*f[a][i]
                        for a in d[1].keys():
                            m += d[1][a]*f[a][j]
                        for a in d[2].keys():
                            m += d[2][a]*f[a][k]
                        ans = min(ans,m)
    print(ans)



def E():
    return


def F():
    return


def G():
    return


def H():
    return


if __name__ == "__main__":
    A()

Solution (Python):
n = int(input())
if n > 999:
    print('ABD')
else:
    print('ABC')

Solution (Python):


n = int(input())

if n <= 999:
    print("ABC")
else:
    print("ABD")

Solution (Python):
n=int(input())
a=n//1000
if a==0:
    print("ABC")
else:
    print("ABD")

Solution (Python):
N = int(input())

if N <= 999:
    print("ABC")
else:
    print("ABD")

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

Solution (Python):
N = int(input())
if N >= 1000:
  print("ABD")
else:
  print("ABC")

Solution (Python):
print("ABC" if int(input())<1000 else "ABD")

Solution (Python):
n = int(input())
print("ABC" if n < 1000 else "ABD")

Solution (Python):

N = int(input())

if N <= 999:
    print('ABC')
else:
    print('ABD')

Solution (Python):
n = int(input())
if n < 1000:
    print("ABC")
else:
    print("ABD")

Solution (Python):
n=int(input())
if n<1000:
	print("ABC")
else: print("ABD")

Solution (Python):
n = int(input())

if n > 999:
  print("ABD")
else:
  print("ABC")

Solution (Python):
N = int(input(' '))

def calc1(N):
  if N <= 999:
    return 'ABC' 
  else:
    return 'ABD' 

print(calc1(N))

Solution (Python):
n = int(input())
if n < 1000:
    print("ABC")
else:
    print("ABD")

Solution (Python):
N = int(input())
if(N>=1000):
  print('ABD')
else:
  print('ABC')

Solution (Python):
n = int(input())

if n < 1000:
    a = 'ABC'
else:
    a ='ABD'
    
print(a)

Solution (Python):
N = int(input())
if N >= 1000: print('ABD')
else: print('ABC')

Solution (Python):
print("AABBDC"[int(input())<1000::2])

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

Solution (Python):
N = int(input())
if(N <= 999):
    print("ABC")
else:
    print("ABD")

Solution (Python):
print('ABD'if int(input())>999else'ABC')

Solution (Python):
n = int(input())

if n >= 1000:
    print("ABD")
else:
    print("ABC")

Solution (Python):
a=int(input())
print("ABC" if a < 1000 else "ABD")

Solution (Python):
N=int(input())
if N <= 999 :
  print("ABC")
else :
  print("ABD")

Solution (Python):
print('ABC') if int(input())<1000 else print('ABD')

Solution (Python):
print("AB"+"CD"[int(input())//1000])

Solution (Python):
N = int(input())
if (N<=999):
    print("ABC")
else:
    print("ABD")

Solution (Python):
print("ABC") if int(input())<1000 else print("ABD")

Solution (Python):
N = int(input())
if N<=999:
    print('ABC')
else:
    print('ABD')

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

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

Solution (Python):
N = int(input())
if N > 999:
    print("ABD")
else:
    print("ABC")

Solution (Python):
n = int(input())

if (n <= 999 ):
    print("ABC")
else:
    print("ABD")

Solution (Python):
def read():
    return raw_input()


def write(message):
    import sys
    print message
    sys.stdout.flush()


if __name__ == '__main__':
    N = int(read())
    write("ABD" if N > 999 else "ABC")

Solution (Python):
print("ABC" if int(input())<=999 else "ABD")

Solution (Python):
contest = int(input())

if contest <= 999:
    print("ABC")
else:
    print("ABD")

Solution (Python):
n = int(input())

if n <= 999:
    print("ABC")
else:
    print("ABD")

Solution (Python):
print('ABC' if int(input())<1000 else 'ABD')

Solution (Python):
A=int(input())
if A<1000 :
    print("ABC")
else :
    print("ABD")

Solution (Python):
N = int(input())

if N < 1000:
    print("ABC")
else:
    print("ABD")

Solution (Python):
N=input()
if int(N)<=999:
    print('ABC')
else:
    print('ABD')

Solution (Python):
N = int(input())
print("ABC" if N < 1000 else "ABD")

Solution (Python):
a = int(input())
if a<1000:
  print("ABC")
else:
  print("ABD")

Solution (Python):
n=int(input())
if n >=1000:
    print("ABD")
else:
    print("ABC")

Solution (Python):
N = int(input())

if N <= 999:
    print('ABC')
else:
    print('ABD')

Solution (Python):
N = int(input())
if N <= 999:
    print("ABC")
else:
    print("ABD")

Solution (Python):
if(int(input()) < 1000):
  print("ABC")
else:
  print("ABD")

Solution (Python):
N = int(input())
print('ABD' if N >= 1000 else 'ABC')

Solution (Python):
n = int(input())

if n<1000:
    print("ABC")
else:
    print("ABD")

Solution (Python):
def solve(string):
    return "ABC" if int(string) < 1000 else "ABD"


if __name__ == '__main__':
    print(solve(input()))

Solution (Python):
print('ABC' if int(input()) < 1000 else 'ABD')

Solution (Python):
n=int(input())
if n<1000:
  print("ABC")
else:
  print("ABD")

Solution (Python):
if int(input()) > 999:
  print("ABD")
else:
  print("ABC")

Solution (Python):
n=int(input())
if n>=1000:
  print("ABD")
else:
  print("ABC")

Solution (Python):
n = int(input())
if n >= 1000:
    print("ABD")
else :
    print("ABC")

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

Solution (Python):
def abd(N: int) -> str:
    return 'ABC' if N < 1000 else 'ABD'


if __name__ == "__main__":
    N = int(input())
    ans = abd(N)
    print(ans)

Solution (Python):
N = int(input())
if(N < 1000):
  print("ABC")
else:
  print("ABD")

Solution (Python):
N = int(input())
if N <= 999:
    print('ABC')
else:
    print('ABD')

Solution (Python):
a=int(input())
if a<1000:
  print("ABC")
else:
  print("ABD")

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

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

Solution (Python):
N = int(input())
print("ABC" if N <= 999 else "ABD")

Solution (Python):
print("AB"+"CCCCD"[len(input())])

Solution (Python):
N = int(input())
if N < 1000:
  print("ABC")
else:
  print("ABD")

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

Solution (Python):
N = int(input())
if N<=999:
    print("ABC")
else:
    print("ABD")

Solution (Python):
n = int(input())
if n <= 999:
    print("ABC")
else:
    print("ABD")

Solution (Python):
N = int(input())
print("ABC") if N < 1000 else print("ABD")

Solution (Python):
N = int(input())
if N <= 999:
    print('ABC')
else:
    print('ABD')

Solution (Python):
N = int(input())
if N>999:
  print('ABD')
else:
  print('ABC')

Solution (Python):

N=int(input())

if N<1000:
    print("ABC")
else:
    print("ABD")

Solution (Python):
N = int(input())
if(N < 1000):
  print("ABC")
else:
  print("ABD")

Solution (Python):
N=int(input())
if N<=999:
  print("ABC")
else:
  print("ABD")

Solution (Python):
print('ABC' if int(input())<1000 else 'ABD')

Solution (Python):
print("ABC" if int(input()) <= 999 else "ABD")

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

Solution (Python):
N = int(input())

if N<=999:print('ABC')
else:print('ABD')

Solution (Python):
n = int(input())
if(n > 999):
	print("ABD")
else:
	print("ABC")

Solution (Python):
N=int(input())
if N<1000:
  print("ABC")
else:
  print("ABD")

Solution (Python):
print('AB'+'CD'[len(input())>3])

Solution (Python):

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

Solution (Python):
N = int(input())
if N > 999:
    print("ABD")
else:
    print("ABC")

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