#include <iostream>
using namespace std;

int main(){
	int n, d;
	cin >> n >> d;
	if(n > d){
		cout << string(d, 'A') << string(n - d, 'C') << endl;
		return 0;
	}
	string s = string(max(0, n - (d - n)), 'A') + string(max(0, d - n), 'B');
	cout << s << string(n - s.size(), 'C') << endl;
}