#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
#include <random>
#include <cassert>
using namespace std;

#define rep(i, N) for (int i = 0; i < N; i++)
#define pb push_back

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<int, ll> i_ll;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
typedef vector<int> vi;
struct edge { int v; ll w; };

const int MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;
ll INF = INT_MAX;

int main() {
	int N, D; cin >> N >> D;
	rep(i, N) {
		if (0 <= D - 1 && D - 1 <= (N - i - 1) * 2) {
			cout << 'A';
			D -= 1;
		}
		else if (0 <= D - 2 && D - 2 <= (N - i - 1) * 2) {
			cout << 'B';
			D -= 2;
		}
		else cout << 'C';
	}
	cout << endl;
}