AtCoder ABC #099 A - ABD

abc099-a.cpp

#include <algorithm>
#include <cstdio>
#include <iostream>
#include <queue>
#include <string>

using namespace std;

int n;

void solve() {
  if (n > 999) {
    cout << "ABD" << endl;
  } else {
    cout << "ABC" << endl;
  }
}

int main() {
  cin >> n;
  solve();
  return 0;
}