#include <bits/stdc++.h>
#define FOR(i,bg,ed) for(ll i=(bg);i<(ed);i++)
#define REP(i,n) FOR(i,0,n)
#define MOD 1000000007
#define int long long
using namespace std;
typedef long long ll;
typedef vector<vector<ll>> mat;
const int INF = 1e9;



signed main()
{
    int N, D;

    cin >> N >> D;

    set<string> ans;
    for (int C=0; C<=N; C++) {
        int A = N - D + C;
        int B = D - 2 * C;

        if (A < 0 || B < 0) continue;

        string kouho = "";
        REP(i,B) kouho += 'A';
        REP(i,C) kouho += 'B';
        REP(i,A) kouho += 'C';

        ans.insert(kouho);
    }

    cout << *ans.begin() << endl;
}