#include <iostream>
#include <string>
#include <vector>
using namespace std;

int main() {
  int N, D;
  cin >> N >> D;

  int d = D - 1;
  vector<char> s(N);
  for (int i = N - 1; i >= 0; i--) {
    if (d > i) {
      s[i] = 'B';
      d -= 2;
    } else if (d == i) {
      s[i] = 'A';
      d--;
    } else {
      s[i] = 'C';
    }
  }

  for (int i = 0; i < N; i++) {
    cout << s[i];
  }
  cout << endl;

  return 0;
}