#include <bits/stdc++.h>
using namespace std;
int main() {
  int k, x, n, m;
  cin >> k >> x >> n >> m;
  for (int a1 = 0; a1 < 2; a1++)
    for (int b1 = 0; b1 < 2; b1++)
      for (int r1 = 0; r1 * 2 + a1 + b1 <= n; r1++)
        for (int a2 = 0; a2 < 2; a2++)
          for (int b2 = 0; b2 < 2; b2++)
            for (int r2 = 0; r2 * 2 + a2 + b2 <= m; r2++) {
              int aa[51], bb[51], rr[51];
              aa[1] = a1;
              aa[2] = a2;
              bb[1] = b1;
              bb[2] = b2;
              rr[1] = r1;
              rr[2] = r2;
              int ok = 1;
              for (int i = 3; i <= k; i++) {
                aa[i] = aa[i - 2];
                bb[i] = bb[i - 1];
                rr[i] = rr[i - 1] + rr[i - 2] + bb[i - 2] * aa[i - 1];
                if (rr[i] > x) {
                  ok = 0;
                  break;
                }
              }
              if (ok && rr[k] == x) {
                if (a1) printf("C");
                for (int j = 0; j < r1; j++) printf("AC");
                for (int j = 0; j < n - r1 * 2 - a1 - b1; j++) printf("D");
                if (b1) printf("A");
                printf("\n");
                if (a2) printf("C");
                for (int j = 0; j < r2; j++) printf("AC");
                for (int j = 0; j < m - r2 * 2 - a2 - b2; j++) printf("D");
                if (b2) printf("A");
                printf("\n");
                return 0;
              }
            }
  printf("Happy new year!\n");
  return 0;
}
