#include <bits/stdc++.h>
using namespace std;
#include <atcoder/fenwicktree>

using ll = long long;
#define rep(i, n) for(int i = 0; i < n; i++)

int main() {
	int N, d;
	cin >> N >> d;
	string s;
	if(N > d) {
		s = string(d, 'A') + string(N - d, 'C');
	}
	else {
		int d1 = d - N;
		s = string(N - d1, 'A') + string(d1, 'B'); 
	}
	cout << s << endl;
}