#include <bits/stdc++.h>
#define rep(i,n) for(int i=(0);i<(n);i++)

using namespace std;

typedef long long ll;
typedef unsigned long long ull;

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);

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

	string ans;
	if(d <= n){
		rep(i, d) ans.push_back('A');
		rep(i, n - d) ans.push_back('C');
	}else{
		rep(i, 2 * n - d) ans.push_back('A');
		rep(i, d - n) ans.push_back('B');
	}

	cout << ans << endl;
}