#include <bits/stdc++.h>
using namespace std;
struct paraula {
  int AC;
  int CC;
  int AA;
};
int main() {
  int k, x, n, m;
  cin >> k >> x >> n >> m;
  --k;
  vector<paraula> vp;
  bool trobat = false;
  for (int ACA = 0; ACA < n; ACA++) {
    for (int ACB = 0; ACB < m; ACB++) {
      for (int AAA = 0; AAA < 2; AAA++) {
        for (int AAB = 0; AAB < 2; AAB++) {
          for (int CCA = 0; CCA < 2; CCA++) {
            for (int CCB = 0; CCB < 2; CCB++) {
              if (trobat) continue;
              if (2 * ACA + CCA + AAA > n) continue;
              if (2 * ACB + CCB + AAB > m) continue;
              bool pot = true;
              vp = vector<paraula>(k + 1);
              vp[0].AA = AAA;
              vp[0].CC = CCA;
              vp[0].AC = ACA;
              vp[1].AA = AAB;
              vp[1].CC = CCB;
              vp[1].AC = ACB;
              for (int pos = 2; pos <= k; ++pos) {
                vp[pos].AA = vp[pos - 1].AA;
                vp[pos].CC = vp[pos - 2].CC;
                vp[pos].AC = vp[pos - 1].AC + vp[pos - 2].AC +
                             vp[pos - 2].AA * vp[pos - 1].CC;
                if (vp[pos].AC > x) {
                  pot = false;
                  break;
                }
              }
              if (pot && vp[k].AC == x) {
                trobat = true;
                int restA = n - (2 * ACA + CCA + AAA);
                int restB = m - (2 * ACB + CCB + AAB);
                if (CCA) cout << 'C';
                for (int auxiliar = 0; auxiliar < restA; auxiliar++)
                  cout << 'X';
                for (int auxiliar = 0; auxiliar < ACA; auxiliar++) cout << "AC";
                if (AAA) cout << 'A';
                cout << endl;
                if (CCB) cout << 'C';
                for (int auxiliar = 0; auxiliar < restB; auxiliar++)
                  cout << 'X';
                for (int auxiliar = 0; auxiliar < ACB; auxiliar++) cout << "AC";
                if (AAB) cout << 'A';
                cout << endl;
              }
            }
          }
        }
      }
    }
  }
  if (!trobat) cout << "Happy new year!" << endl;
}
