#include <bits/stdc++.h>
using namespace std;
int k, x, n, m;
int f(int x) {
  if (x > 0) return 1;
  return 0;
}
void print(int cnt1, int cnt2, int t) {
  if (t & 8) printf("C");
  for (int i = 1; i <= cnt1; i++) printf("AC");
  for (int i = 2 * cnt1 + 1 + f(t & 8); i <= n - f(t & 4); i++) printf("B");
  if (t & 4) printf("A");
  printf("\n");
  if (t & 2) printf("C");
  for (int i = 1; i <= cnt2; i++) printf("AC");
  for (int i = 2 * cnt2 + 1 + f(t & 2); i <= m - f(t & 1); i++) printf("B");
  if (t & 1) printf("A");
  printf("\n");
}
int main() {
  scanf("%d%d%d%d", &k, &x, &n, &m);
  int cnt1, cnt2, cnt3;
  for (int i = 0; i <= n / 2; i++)
    for (int j = 0; j <= m / 2; j++)
      for (int t = 0; t < 16; t++) {
        if (i * 2 + f(t & 8) + f(t & 4) > n) continue;
        if (j * 2 + f(t & 2) + f(t & 1) > m) continue;
        cnt1 = i, cnt2 = j;
        bool fin = 1;
        for (int p = 3; p <= k; p++) {
          cnt3 = cnt1 + cnt2;
          if (p == 3)
            cnt3 += (f(t & 4) & f(t & 2));
          else if (p % 2 == 0)
            cnt3 += (f(t & 8) & f(t & 1));
          else if (p % 2 == 1)
            cnt3 += (f(t & 2) & f(t & 1));
          cnt1 = cnt2, cnt2 = cnt3;
          if (cnt2 > x) {
            fin = 0;
            break;
          }
        }
        if (cnt2 != x) fin = 0;
        if (fin) {
          print(i, j, t);
          return 0;
        }
      }
  printf("Happy new year!\n");
  return 0;
}
