#include <bits/stdc++.h>
using namespace std;
int main() {
  int k, x, n, m;
  scanf("%d%d%d%d", &k, &x, &n, &m);
  for (int f1 = 0; f1 <= 1; f1++) {
    for (int f2 = 0; f2 <= 1; f2++) {
      for (int f3 = 0; f3 <= 1; f3++) {
        int h1 = n, h2 = m;
        if (f1) h1--;
        if (f1 || f3) h2--;
        if (f2) h1--, h2--;
        if (!f2 && f3) h2--;
        if (h1 < 0 || h2 < 0) continue;
        for (int i = 0; i <= h1 / 2; i++) {
          for (int j = 0; j <= h2 / 2; j++) {
            long long las1 = i, las2 = j;
            for (int t = 3; t <= k; t++) {
              long long tmp1 = las2, tmp2 = las1 + las2;
              las1 = tmp1, las2 = tmp2;
              if (t == 3 && f1) las2++;
              if (t >= 4 && t % 2 == 0 && f2) las2++;
              if (t >= 4 && t % 2 == 1 && f3) las2++;
            }
            if (las2 == x) {
              if (f2) printf("C");
              for (int h = 1; h <= i; h++) printf("AC");
              for (int h = 1; h <= h1 - 2 * i; h++) printf("Z");
              if (f1) printf("A");
              printf("\n");
              if (f1 || f3) printf("C");
              for (int h = 1; h <= j; h++) printf("AC");
              for (int h = 1; h <= h2 - 2 * j; h++) printf("Z");
              if (f2 || f3) printf("A");
              printf("\n");
              return 0;
            }
          }
        }
      }
    }
  }
  printf("Happy new year!\n");
  return 0;
}
