#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <math.h>
#include <cmath>
#include <limits.h>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <functional>
#include <stdio.h>
using namespace std;

long long MOD = 1000000007;

int main() {
    int N,D;
    cin >> N >> D;
    string S(N,'A');
    char c = N < D ? 'B' : 'C';

    for ( int i = 0; i < abs(N-D); i++ ) {
        S[N-1-i] = c;
    }

    cout << S << endl;
    return 0;
}