#include <iostream>
#include <fstream>
#include <cstdio>
#include <cmath>
#include <vector>
#include <cstring>
#include <string>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <algorithm>
using namespace std;

#define REP(i,n) for(int i=0; i<n; ++i)
#define FOR(i,a,b) for(int i=a; i<=b; ++i)
#define FORR(i,a,b) for (int i=a; i>=b; --i)
#define ALL(c) (c).begin(), (c).end()

typedef long long ll;
typedef vector<int> VI;
typedef vector<ll> VL;
typedef vector<VI> VVI;
typedef pair<int,int> P;
typedef pair<ll,ll> PL;

int main() {
	int n, d;
	cin >> n >> d;
	string ans;
	if (n >= d){
		REP(i,d) ans += 'A';
		REP(i,n-d) ans += 'C';
	}else{
		int x = d - n;
		REP(i,n-x) ans += 'A';
		REP(i,x) ans += 'B';
	}
	cout << ans << endl;
    return 0;
}