#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using ul = unsigned long;
using ull = unsigned long long;

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);

	int n, d;
	cin >> n >> d;

	string res;

	if (d == 0)
		res = string(n, 'C');
	else if (d == n)
		res = string(n, 'A');
	else if (d == n * 2)
		res = string(n, 'B');
	else if (d == 1)
	{
		res = "A";
		if (n > 1)
			res += string(n - 1, 'C');
	}
	else if (d > n)
		res = string(n * 2 - d, 'A') + string(d - n, 'B');
	else
		res = string(d, 'A') + string(n - d, 'C');

	cout << res << "\n";

	return 0;
}