#include <bits/stdc++.h>
using namespace std;
long long k, T, n, m;
int main() {
  cin >> k >> T >> n >> m;
  for (int i = 0; i < (1 << 4); i++) {
    bool l1 = i & 1, t1 = i & 2, l2 = i & 4, t2 = i & 8;
    for (int x = 0; 2 * x <= (n - l1 - t1); x++) {
      for (int y = 0; 2 * y <= (m - l2 - t2); y++) {
        bool tt1 = t1, tt2 = t2, tl1 = l1, tl2 = l2;
        long long c1 = x, c2 = y;
        for (int j = 3; j <= k; j++) {
          c1 = c1 + c2 + (tt1 && tl2);
          tt1 = tt2;
          swap(c1, c2);
          swap(tt1, tt2);
          swap(tl1, tl2);
        }
        if (c2 == T) {
          string s1 = "";
          int sz = 0;
          if (i & 1) {
            s1 += "C";
            sz++;
          }
          for (int j = 0; j < x; j++) {
            s1 += "AC";
            sz += 2;
          }
          while (sz < n - 1) {
            s1 += "Z";
            sz++;
          }
          if (sz == n - 1) s1 += (i & 2) ? "A" : "Z";
          string s2 = "";
          sz = 0;
          if (i & 4) {
            s2 += "C";
            sz++;
          }
          for (int j = 0; j < y; j++) {
            s2 += "AC";
            sz += 2;
          }
          while (sz < m - 1) {
            s2 += "Z";
            sz++;
          }
          if (sz == m - 1) s2 += (i & 8) ? "A" : "Z";
          cout << s1 << endl;
          cout << s2 << endl;
          return 0;
        }
      }
    }
  }
  printf("Happy new year!\n");
  return 0;
}
