#define _GLIBCXX_DEBUG
#define ll long long
#include <bits/stdc++.h>
using namespace std;
using Graph = vector<vector<int>>;

int main(){
  int N, D; cin >> N >> D;
  string ans = "";
  int i = 0;
  while(i < N){
    if(D == 0) ans += "C";
    else if((N-i)*2 == D){ ans += "B"; D -= 2;}
    else {ans += "A"; D--;}
    i++;
  }
  cout << ans << endl;
}