#include <bits/stdc++.h>
using namespace std;
template <class A, class B>
A cvt(B x) {
  stringstream ss;
  ss << x;
  A y;
  ss >> y;
  return y;
}
char cf[51], cl[51];
long long ac[51], m1[51], m2[51];
int construct(int n, char first, char last, int num, string &s) {
  s = string(n, 'X');
  if (n == 1 && first != last) return 0;
  s[0] = first;
  s[n - 1] = last;
  for (int i = (0); i <= (n - 2); i++) {
    if (s[i] == 'A' || s[i] == 'X') {
      s[i] = 'A';
      if (s[i + 1] == 'C' || s[i + 1] == 'X') {
        num--;
        s[i + 1] = 'C';
      } else
        break;
    }
    if (num == 0) break;
  }
  return num == 0;
}
int gen(int k, string s1, string s2) {
  for (int i = (3); i <= (k); i++) {
    string s = s1 + s2;
    s1 = s2;
    s2 = s;
  }
  int st = 0;
  cout << s2 << endl;
  for (int i = (0); i <= (s2.size() - 2); i++) {
    if (s2[i] == 'A' && s2[i + 1] == 'C') st++;
  }
  return st;
}
int main() {
  int k, x, n, m;
  scanf("%d %d %d %d", &k, &x, &n, &m);
  string acx = "ACY";
  for (int i1 = 0; i1 < (3); i1++)
    for (int i2 = 0; i2 < (3); i2++)
      for (int n1 = (0); n1 <= (n / 2); n1++) {
        string s1;
        if (!construct(n, acx[i1], acx[i2], n1, s1)) continue;
        for (int j1 = 0; j1 < (3); j1++)
          for (int j2 = 0; j2 < (3); j2++)
            for (int n2 = (0); n2 <= (m / 2); n2++) {
              string s2;
              if (!construct(m, acx[j1], acx[j2], n2, s2)) continue;
              cf[1] = acx[i1];
              cl[1] = acx[i2];
              cf[2] = acx[j1];
              cl[2] = acx[j2];
              ac[1] = n1;
              ac[2] = n2;
              for (int a = (3); a <= (k); a++) {
                cf[a] = cf[a - 2];
                cl[a] = cl[a - 1];
                ac[a] = ac[a - 2] + ac[a - 1];
                if (cl[a - 2] == 'A' && cf[a - 1] == 'C') ac[a]++;
              }
              if (ac[k] == x) {
                cout << s1 << endl;
                cout << s2 << endl;
                goto found;
              }
            }
      }
  printf("Happy new year!\n");
found:;
  return 0;
}
