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

using namespace std;

int main(){
	int n, d;
	cin >> n >> d;
	
	string res = "";
	string res_back = "";
	for(int i=0; i<d; i++) res.push_back('A');
	n -= res.length();
	while(n != 0){
		if(n == 1) {
			res_back.push_back('C');
			break;
		}
		if(n < 0){
			res.pop_back();
			res.pop_back();
			res_back.push_back('B');
			n += 1;
		}else{
			res_back.push_back('C');
			n -= 1;
		}
	}
	cout << res << res_back<<  endl;
			
}