#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for(ll i = 0, i##_len = (n); i < i##_len; i++)
#define reps(i, s, n) for(ll i = (s), i##_len = (n); i < i##_len; i++)
#define rrep(i, n) for(ll i = (n) - 1; i >= 0; i--)
#define rreps(i, e, n) for(ll i = (n) - 1; i >= (e); i--)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) ((ll)(x).size())
#define len(x) ((ll)(x).length())
#define endl "\n"

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    // ifstream in("input.txt");
    // cin.rdbuf(in.rdbuf());
    ll n, d;
    cin >> n >> d;
    vector<ll> cnt(3, 0);
    rep(c, 2 * n + 1) {
        ll a = n - d + c;
        ll b = d - 2 * c;
        if ((a >= 0) && (b >= 0) && (c >= 0)) {
            cnt[0] = a;
            cnt[1] = b;
            cnt[2] = c;
            break;
        }
    }
    string ans = "";
    rep(i, cnt[1]) ans += 'A';
    rep(i, cnt[2]) ans += 'B';
    rep(i, cnt[0]) ans += 'C';
    cout << ans << endl;
    return 0;
}