/* -*- coding: utf-8 -*-
 *
 * 501.cc: No.501 穴と文字列 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

/* typedef */

/* global variables */

/* subroutines */

/* main */

int main() {
  int n, d;
  cin >> n >> d;

  while (n > 0) {
    int ch;
    if (d >= n * 2) ch = 'B', d -= 2;
    else if (d == 0) ch = 'C';
    else ch = 'A', d--;
    n--;
    putchar(ch);
  }
  putchar('\n');
  return 0;
}