#include <bits/stdc++.h>
using namespace std;
bool doable(int len, int occ, int fro, int bac, string &s) {
  s.resize(len, 'B');
  if (len == 1) {
    if (occ || fro != bac)
      return 0;
    else {
      s[0] = 'A' + fro;
      return 1;
    }
  }
  s[0] = 'A' + fro;
  s[len - 1] = 'A' + bac;
  int here = 0;
  for (int i = (1); i <= (len - 2); ++i)
    if (here < occ) {
      if (s[i - 1] == 'A') {
        s[i] = 'C';
        here++;
      } else
        s[i] = 'A';
    }
  for (int i = (0); i <= (len - 2); ++i)
    if (s[i] == 'A' && s[i + 1] == 'C') occ--;
  return (occ == 0);
}
int main() {
  ios_base::sync_with_stdio(0);
  int k, x, n, m;
  cin >> k >> x >> n >> m;
  for (int occ1 = (0); occ1 <= (n / 2); ++occ1)
    for (int occ2 = (0); occ2 <= (m / 2); ++occ2)
      for (int fro1 = (0); fro1 <= (2); ++fro1)
        for (int fro2 = (0); fro2 <= (2); ++fro2)
          for (int bac1 = (0); bac1 <= (2); ++bac1)
            for (int bac2 = (0); bac2 <= (2); ++bac2) {
              int x1 = occ1, x2 = occ2, f1 = fro1, f2 = fro2, b1 = bac1,
                  b2 = bac2;
              for (int i = (1); i <= (k - 2); ++i) {
                int x3 = x1 + x2 + ((b1 == 0) && (f2 == 2)), f3 = f1, b3 = b2;
                x1 = x2;
                x2 = x3;
                f1 = f2;
                f2 = f3;
                b1 = b2;
                b2 = b3;
                if (x2 > x) break;
              }
              if (x2 == x) {
                string s1, s2;
                if (doable(n, occ1, fro1, bac1, s1) &&
                    doable(m, occ2, fro2, bac2, s2)) {
                  cout << s1 << '\n' << s2;
                  return 0;
                }
              }
            }
  cout << "Happy new year!";
  return 0;
}
