#include <iostream>
#include <algorithm>
#include <utility>
#include <string>

using namespace std;

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

	string s;
	if (d <= n) {
		s = string(d, 'A') + string(n - d, 'C');
	} else {
		s = string(2 * n - d, 'A') + string(d - n, 'B');
	}

	cout << s << endl;
	return 0;
}