#include <bits/stdc++.h>
using namespace std;
int k, x, n, m;
string make(int ac, int st, int en, int len) {
  string ret = "";
  if (st) ret += 'C';
  for (int i = 0; i < ac; i++) {
    ret += 'A';
    ret += 'C';
  }
  while (ret.size() < len - en) ret += 'B';
  if (en) ret += 'A';
  return ret;
}
int cnt[55], st[55], en[55];
bool check(int ac1, int ac2, int k1, int k2, int k3, int k4) {
  cnt[0] = ac1;
  st[0] = k1;
  en[0] = k2;
  cnt[1] = ac2;
  st[1] = k3;
  en[1] = k4;
  for (int i = 2; i < k; i++) {
    cnt[i] = cnt[i - 2] + cnt[i - 1];
    if (en[i - 2] && st[i - 1]) cnt[i]++;
    if (cnt[i] > x) return false;
    st[i] = st[i - 2];
    en[i] = en[i - 1];
  }
  return (cnt[k - 1] == x);
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cin >> k >> x >> n >> m;
  for (int i = 0; i <= n; i++)
    for (int j = 0; j <= m; j++)
      for (int k1 = 0; k1 <= 1; k1++)
        for (int k2 = 0; k2 <= 1; k2++)
          for (int k3 = 0; k3 <= 1; k3++)
            for (int k4 = 0; k4 <= 1; k4++) {
              string cur1 = make(i, k1, k2, n);
              string cur2 = make(j, k3, k4, m);
              if (cur1.size() != n) continue;
              if (cur2.size() != m) continue;
              if (check(i, j, k1, k2, k3, k4)) {
                cout << cur1 << '\n' << cur2 << '\n';
                return 0;
              }
            }
  cout << "Happy new year!" << '\n';
  return 0;
}
