#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<ll> VL;
typedef vector<VL> VVL;
typedef pair<int, int> PII;

#define FOR(i, a, n) for (ll i = (ll)a; i < (ll)n; ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(x) x.begin(), x.end()
#define MP make_pair
#define PB push_back
#define MOD 1000000007
#define INF (1LL<<30)
#define LLINF (1LL<<60)
#define PI 3.14159265359
#define EPS 1e-12
#define int ll

signed main(void)
{
  int n, d;
  cin >> n >> d;

  string ans;
  if(d < n) {
    REP(i, d) ans += 'A';
    REP(i, n-d) ans += 'C';
  } else if(d == n) {
    REP(i, n) ans += 'A';
  } else if(d > n) {
    int tmp = n-(d-n);
    REP(i, tmp) ans += 'A';
    REP(i, d-n) ans += 'B';
  }
  cout << ans << endl;

  return 0;
}