#include <bits/stdc++.h>

using namespace std;

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

  string ret = string(N, '~');

  for(int A = 0; A <= N; A++) {
    int sub = D - A;
    if(sub < 0) continue;
    if(sub % 2 == 1) continue;
    sub /= 2;
    if(N - A - sub < 0) continue;
    ret = min(ret, string(A, 'A') + string(sub, 'B') + string(N - A - sub, 'C'));
  }

  cout << ret << endl;
}