#include <bits/stdc++.h>
using namespace std;
const int tp9 = 1000 * 1000 * 1000;
const int MAX = 100;
int k, x, n, m;
char let[] = {'A', 'C', 'B'};
char s1[MAX + 4], s2[MAX + 4];
inline bool good(int k1, int k2, int l, char s[], int n) {
  for (int i = 0; i <= MAX + 2; ++i) s[i] = '\0';
  bool res = false;
  s[1] = let[k1];
  s[n] = let[k2];
  if (n == 2) {
    if (k1 == 0 && k2 == 1) {
      if (l == 1)
        return true;
      else
        return false;
    } else {
      if (l == 0)
        return true;
      else
        return false;
    }
  }
  for (int i = 2; i <= n; ++i) {
    if (!s[i] && l > 0) {
      if (s[1] == 'A')
        s[i] = (i % 2 == 0 ? 'C' : 'A');
      else
        s[i] = (i % 2 == 0 ? 'A' : 'C');
    } else if (!s[i] && l <= 0)
      s[i] = let[2];
    if (s[i - 1] == 'A' && s[i] == 'C') --l;
    if (l <= 0) res = true;
  }
  if (l <= 0) res = true;
  return res;
}
inline bool check(int l1, int l2, int k1, int k2, int k3, int k4) {
  int f, s, n = 0;
  int d1 = l1, d2 = l2;
  for (int i = 3; i <= k; ++i) {
    n = l1 + l2 + (k2 == 0 && k3 == 1);
    f = k1;
    s = k4;
    l1 = l2;
    k1 = k3;
    k2 = k4;
    l2 = n;
    k3 = f;
    k4 = s;
    if (n > tp9) return false;
  }
  if (n == x) return true;
  return false;
}
int main() {
  cin >> k >> x >> n >> m;
  for (int k1 = 0; k1 <= 2; ++k1) {
    for (int k2 = 0; k2 <= 2; ++k2) {
      for (int l1 = 0;
           good(k1, (n > 1 ? k2 : k1), l1, s1, n) || (l1 == 0 && n == 2);
           ++l1) {
        for (int k3 = 0; k3 <= 2; ++k3) {
          for (int k4 = 0; k4 <= 2; ++k4) {
            for (int l2 = 0;
                 good(k3, (m > 1 ? k4 : k3), l2, s2, m) || (l2 == 0 && m == 2);
                 ++l2) {
              if (check(l1, l2, k1, (n > 1 ? k2 : k1), k3, (m > 1 ? k4 : k3)) &&
                  good(k1, (n > 1 ? k2 : k1), l1, s1, n) &&
                  good(k3, (m > 1 ? k4 : k3), l2, s2, m)) {
                cout << s1 + 1;
                cout << endl;
                cout << s2 + 1;
                cout << endl;
                return 0;
              }
            }
          }
        }
      }
    }
  }
  cout << "Happy new year!\n";
}
