#include <bits/stdc++.h>
using namespace std;
long long fib[100];
int k, x, n, m, aa, bb;
char ansa[103], ansb[103];
int calc(int s1, int s2) {
  int a = s1, b = s2, t;
  int ca = 0, cb = 0, sum = 0;
  for (int i = 3; i <= k; ++i) {
    sum = ca + cb;
    if ((a & 2) && !(a & 1) && (b & 8) && (b & 4)) ++sum;
    t = b, b = (a & (3 << 2)) | (b & 3);
    a = t, t = cb, cb = sum, ca = t;
  }
  return sum;
}
bool product(int t, int code, char *p, int len) {
  int pp = 1;
  if (len == 1 && ((code >> 2) & 3) != (code & 3)) return false;
  if (len == 2 && code == 11) --t;
  if ((code >> 2) == 3)
    p[0] = 'C';
  else if ((code >> 2) == 2)
    p[0] = 'A';
  else
    p[0] = 'B';
  if ((code >> 2) == 2 && t && len > 2) --t, p[pp++] = 'C';
  while (pp < len - 2 && t) {
    p[pp++] = 'A';
    p[pp++] = 'C';
    --t;
  }
  p[len] = '\0';
  if ((code & 3) == 3)
    p[len - 1] = 'C';
  else if ((code & 3) == 2)
    p[len - 1] = 'A';
  else
    p[len - 1] = 'B';
  if (pp <= len - 2 && p[len - 1] == 'C' && t) --t, p[len - 2] = 'A', --len;
  while (pp < len - 1) p[pp++] = 'B';
  if (t) return false;
  return true;
}
bool calc2(int ret) {
  int p = x - ret;
  for (int a = 0; a <= 50; ++a) {
    int pp = p - a * fib[k - 2];
    if (pp % fib[k - 1] != 0) continue;
    if (product(a, aa, ansa, n) && product(pp / fib[k - 1], bb, ansb, m))
      return true;
  }
  return false;
}
int main() {
  fib[0] = 0;
  fib[1] = fib[2] = 1;
  for (int i = 3; i <= 50; ++i) fib[i] = fib[i - 1] + fib[i - 2];
  while (~scanf("%d%d%d%d", &k, &x, &n, &m)) {
    bool fla = true;
    for (aa = 0; aa < 16 && fla; ++aa)
      for (bb = 0; bb < 16; ++bb) {
        if (calc2(calc(aa, bb))) {
          printf("%s\n%s\n", ansa, ansb), fla = false;
          break;
        }
      }
    if (fla) puts("Happy new year!");
  }
}
