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

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

Solution (Python):
import math
import queue
import bisect
import heapq
import time
import itertools

mod = int(1e9+7)

def swap(a,b):
    return (b,a)

def my_round(a,dig=0):
    p = 10 ** dig
    return (a * p * 2 + 1) // 2 / p

def gcd(a,b): 
    if (a<b):
        a,b = swap(a,b)
    if (b==0):
        return a
    else:
        return gcd(b,a%b)

def lcm(a,b): 
    return a/gcd(a,b)*b

def divisors(a): 
    divisors = []
    for i in range(1,int(a**0.5)+1):
        if a%i==0:
            divisors.append(i)
            if i!=a//i:
                divisors.append(a//i)
    return divisors

def is_prime(a): 
    if a<2:
        return False
    elif a==2:
        return True
    elif a%2==0:
        return False
    sqrt_num = int(a**0.5)
    for i in range(3,sqrt_num+1,2):
        if a%i==0:
            return False
    return True

def prime_num(a): 
    pn = [2]
    for i in range(3,int(a**0.5),2):
        prime = True
        for j in pn:
            if i%j==0:
                prime = False
                break
        if prime:
            pn.append(i)
    return pn

def prime_fact(a): 
    sqrt = math.sqrt(a)
    res = []
    i = 2
    if is_prime(a):
        res.append(a)
    else:
        while a!=1:
            while a%i==0:
                res.append(i)
                a //= i
            i += 1
    return res

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

if __name__=='__main__':
    main()

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())

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

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

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

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

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

ans = "ABC"
if N > 999:  
  ans = "ABD"
print(ans)

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

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):
import sys
input = sys.stdin.buffer.readline

def gcd(a: int, b: int):
    """ https://cocodrips.hateblo.jp/entry/2014/03/05/143623
    """
    while b:
        a, b = b, a%b
    return a

def lcm(a: int, b: int):
    return a * b // gcd(a, b)


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


if __name__ == "__main__":
    main()

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

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("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())

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

Solution (Python):
import sys
input = sys.stdin.readline
N = int(input())
ans = "ABC"
if N >= 1000 :
    ans = "ABD"
print(ans)

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

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

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

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

Solution (Python):
import sys

n = int(sys.stdin.readline().rstrip())

def main():
    return 'ABC' if n < 1000 else 'ABD'

if __name__ == '__main__':
    ans = main()
    print(ans)

Solution (Python):
MOD=10**9+7
cnt=0; sum=0


def gs(): return input()
def gi(): return int(input())
def gsmi(): return [int(n) for n in input().split()]

def desc(ar): return sorted(ar,reverse=True)
def printend(s): print(s);import sys;sys.exit()

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

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

keta = len(str(N))

if keta<=3:
    print("ABC")
else:
    print("ABD")

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

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

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

Solution (Python):
import sys
input = sys.stdin.readline
N = int(input())
if N >= 1000:
    print("ABD")
else:
    print("ABC")

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

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

Solution (Python):
import sys
input = sys.stdin.readline
N = int(input())
code = ["ABC", "ABD"]
print(code[N//1000])

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):


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

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

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 1000 <= n <=1998:
    n = n-999
    print("ABD")
else:
    print("ABC")

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

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

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

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):
import math

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

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

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

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

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

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

Solution (Python):
N = int( input() )
print( [ "ABC", "ABD" ][ N>=1000] )

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 <= 999 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):




n1 = input()
n = int(n1)+1

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

Solution (Python):
from collections import Counter,defaultdict,deque
from heapq import heappop,heappush,heapify
import sys,bisect,math,itertools,fractions,pprint
sys.setrecursionlimit(10**8)
mod = 10**9+7
mod2 = 998244353
INF = float('inf')
def inp(): return int(sys.stdin.readline())
def inpl(): return list(map(int, sys.stdin.readline().split()))
def inpln(n): return list(int(sys.stdin.readline()) for i in range(n))

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

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

Solution (Python):
INT = lambda: int(input())
INTM = lambda: map(int,input().split())
STRM = lambda: map(str,input().split())
STR = lambda: str(input())
LIST = lambda: list(map(int,input().split()))
LISTS = lambda: list(map(str,input().split()))
def do():
    n=INT()
    if n<=999:
        print('ABC')
    else:
        print('ABD')
if __name__ == '__main__':
    do()

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

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

Solution (Python):
n=input()
if len(n)==4:
  print("ABD")
else:
  print("ABC")

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

Solution (Python):

import sys


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


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

Solution (Python):

import sys
input = sys.stdin.readline
sys.setrecursionlimit(10**6)

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

Solution (Python):
N = int(input())
print("ABC" if N < 1000 else "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())
print("ABC") if n <= 999 else print("ABD")

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

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

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

if N <= 999:
    ans = 'ABC'
else:
    ans = 'ABD'

print(ans)

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

Solution (Python):
def examA():
    N = I()
    ans = "ABC"
    if N>=1000:
        ans = "ABD"
    print(ans)



import sys,copy,bisect,itertools,heapq,math
from heapq import heappop,heappush,heapify
from collections import Counter,defaultdict,deque
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))
def LSI(): return list(map(str,sys.stdin.readline().split()))
def LS(): return sys.stdin.readline().split()
def SI(): return sys.stdin.readline().strip()
mod = 10**9 + 7
inf = float('inf')

examA()

Solution (Python):

import math




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

Solution (Python):

import sys, math, itertools, heapq, collections, bisect
input = lambda: sys.stdin.buffer.readline().rstrip().decode('utf-8')
sys.setrecursionlimit(10**8)
inf = float('inf')
ans = count = 0

n=int(input())
if 1<=n<=999:
    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("ABD")

else:
    print("ABC")

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

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

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

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

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

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

if 1000 <= n <= 1998: print("ABD")
elif n <= 999: print("ABC")

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

Solution (Python):
print("ABC"if int(input())<=999 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):
import sys
read = sys.stdin.buffer.read
input=lambda :sys.stdin.readline().rstrip()
inputs= sys.stdin.buffer.readlines
INF=float("inf")
MOD=10**9+7
























def main():
	n=int(input())
	ans="ABC"
	if n>999:
		ans="ABD"
	print(ans)
	




if __name__ == '__main__':
	main()

Solution (Python):


def main():
    N = int(input())
    if N > 999:
        print('ABD')
    else:
        print('ABC')

if __name__ == "__main__":
    main()

Solution (Python):
n = int(input().split()[0])
ans = "ABD" if n > 999 else "ABC"
print(ans)

Solution (Python):
from sys import stdin
import fractions

n = int(stdin.readline().rstrip())

if n <1000:
    print("ABC")

else:
    print("ABD")

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

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())

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

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

Solution (Python):



import sys













def main():
    n = int(sys.stdin.readline().rstrip())
    if n < 1000:
        ans = 'ABC'
    else:
        ans = 'ABD'
    
    print(ans)



if __name__ == "__main__":
    
    main()

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

Solution (Python):

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

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

Solution (Python):

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

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

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):
print(format(0xABC000 + int(input(), 16), 'x').upper()[:3])

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

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

Solution (Python):
n=int(input())
print("ABC" if 1<=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):
n=int(input())

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

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

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

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

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

Solution (Python):
n=int(input())
print("AB"+"C"*(n<1000)+"D"*(n>=1000))

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("ABD")
else:
    print("ABC")

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

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

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

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

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

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

print(ans)

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

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

Solution (Python):
n=input()
print("ABD" if len(n)>=4 else "ABC")

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

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

Solution (Python):
n = int(input())
if 1 <= n <= 999:
    print('ABC')
elif 1000 <= n <= 1998:
    print('ABD')

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

if N < 1000:
  print('ABC')
elif N >=1000 and N <= 1998:
  print('ABD')

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

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

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

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

if __name__ == "__main__":
    resolve()

Solution (Python):
N = int(input())
print("ABC" if N//1000 < 1 else "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 <= 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("ABD")
else:
  print("ABC")

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

Solution (Python):
import sys

input = sys.stdin.readline


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


if __name__ == "__main__":
    main()

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):
N = int(input())

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

Solution (Python):
def slove():
    import sys
    input = sys.stdin.readline
    n = int(input().rstrip('\n'))
    print("ABD" if n > 999 else "ABC")


if __name__ == '__main__':
    slove()

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

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

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

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

Solution (Python):
s=input()
a=int(s)
if 1000<=a<=1998:
  print('ABD')
else:
  print('ABC')

Solution (Python):
n = int(input())
if(1 <= 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("ABD")
else:
  print("ABC")

Solution (Python):
def aa099():
    n = int(input())
    print('ABC' if n < 1000 else 'ABD')

aa099()

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

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("ABD")
else:
  print("ABC")

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

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

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

if 0<N<1000:
  print('ABC')

if 999<N<1999:
  print('ABD')

Solution (Python):
if int(input()) >= 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):
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('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):
[print('ABC') if int(input()) < 1000 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())
print('AB'+'CD'[n//1000])

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

Solution (Python):
import sys

if sys.platform =='ios':
    sys.stdin=open('input_file.txt')
    
n=int(input())

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

Solution (Python):
print('ABC' if int(input().strip()) < 1000 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):
N = int(input())
print('ABC' if 1 <= N and N <= 999 else 'ABD')

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

Solution (Python):

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

Solution (Python):
import sys
from collections import defaultdict
sys.setrecursionlimit(200000)
input = sys.stdin.readline

N, = map(int, input().split())

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

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

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

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

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

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

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());print(["ABC","ABD"][n>999])

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

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

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

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

print("AB{0}".format("C" if n//1000 == 0 else "D"))

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

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

Solution (Python):
print(['ABD','ABC'][len(input())<4])

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

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

Solution (Python):

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

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):
n = int(input())

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

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

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

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

else:
  print("ABC")

Solution (Python):
n = int(input())
if 1 <= n <= 999:
  print("ABC")
else:
  print("ABD")

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