#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
#define rep(i,m,n) for(int i=m; i<int(n); ++i)
#define repll(i,m,n) for(ll i=m; i<ll(n); ++i)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define leng(a) int(a.size())
#define fi first
#define se second

template<typename T> bool chmin(T& a, T b){ if(a > b){a = b; return true;} return false; }
template<typename T> bool chmax(T& a, T b){ if(a < b){a = b; return true;} return false; }

template<typename T> T gcd(T a, T b){ return a % b ? gcd(b, a % b) : b; }
template<typename T> T lcm(T a, T b){ return a / gcd(a, b) * b; }

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int N, D;
    cin >> N >> D;

    if(D == 0){
        cout << string(N,'C') << endl;
    }else{
        string ans(N,'Z');
        int a, b, c;
        for(b = 0; 2*b <= D; ++b){
            a = D - 2*b;
            c = N - a - b;
            if(a < 0 || c < 0) continue;
            chmin(ans, string(a,'A') + string(b,'B') + string(c,'C'));
        }
        cout << ans << endl;
    }
    return 0;
}