#include<bits/stdc++.h>
#include<unordered_set>
#include<unordered_map>
using namespace std;


int n;
int d;
int main(){
	cin >> n >> d;
	int cnt2 = 0;
	while (d > n){
		cnt2++;
		n--;
		d -= 2;
	}
	if (d <= n){
		for (int i = 1; i <= d; i++){
			cout << "A";
		}
		for (int i = d + 1; i <= n; i++){
			cout << "C";
		}
		for (int i = 0; i < cnt2; i++){
			cout << "B";
		}
		cout << endl;
		return 0;
	}
	
	return 0;
}