#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <tuple>

using namespace std;

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

	tuple<int, int, int> mx;
	for (int k = 0; k * 2 <= D; k++) {
		int j = D - k * 2;
		int i = N - j - k;
		if (i >= 0) {
			mx = max(mx, make_tuple(j, k, i));
		}
	}
	int j, k, i;
	tie(j, k, i) = mx;
	cout << string(j, 'A');
	cout << string(k, 'B');
	cout << string(i, 'C');
}