#include <iostream>
#include <algorithm>
#include <functional>
#include <string>
#include <climits>
#include <vector>
#include <numeric>
#include <complex>
#include <map>
#include <bitset>
#include <stack>
#include <queue>
#include <set>
using namespace std;

//#define __int64 long long
#define REP(i,a,b) for(int i=a;i<b;i++)
#define rep(i,n) REP(i,0,n)
const int Vec = 4;
const int Vecy[Vec] = {0,-1,0,1};
const int Vecx[Vec] = {1,0,-1,0};
const int Modd = 1000000007;

int main(){
	int n,d;
	int sa;
	char use;
	string ans;
	
	cin >> n >> d;
	
	rep(i,n){
		ans += 'A';
	}
	
	sa = abs(d - n);
	
	if(d - n > 0){
		use = 'B';
	}else{
		use = 'C';
	}
	
	for(int i=0; i<sa; i++){
		ans[n-1-i] = use;
	}
	
	cout << ans << endl;
	
    return 0;
}