#include <algorithm>
#include <iostream>

using namespace std;

int main(int argc, const char* argv[])
{
	int N, D;
	cin >> N >> D;
	char A[] = {'A', 'B', 'C'};
	string s;
	int nB   = max(D - N, 0);
	int nA   = max(min(N - nB, D - nB), 0);
	int nC   = N - nB - nA;
	int nS[] = {nA, nB, nC};
	for (int j = 0; j < 3; j++)
		for (int i = 0; i < nS[j]; i++) s += A[j];
	cout << s << endl;
	return 0;
}