#include <bits/stdc++.h>
long long int a[55], b[55], c[3][55];
int combi[7][3] = {{0, 0, 0}, {1, 0, 0}, {0, 1, 0}, {0, 0, 1},
                   {1, 0, 1}, {0, 1, 1}, {1, 1, 1}};
int nnmm[7][2] = {{0, 0}, {1, 1}, {1, 1}, {0, 2}, {1, 2}, {1, 2}, {2, 2}};
char str1[105], str2[105];
int main() {
  int k, n, m;
  long long int x;
  scanf("%d %lld %d %d", &k, &x, &n, &m);
  a[1] = 1;
  b[2] = 1;
  int i, j;
  for (i = 3; i <= k; i++) {
    a[i] = a[i - 1] + a[i - 2];
    b[i] = b[i - 1] + b[i - 2];
  }
  c[0][3] = 1;
  for (i = 4; i <= k; i++) {
    for (j = 0; j < 3; j++) c[j][i] = c[j][i - 1] + c[j][i - 2];
    if (i % 2 == 0)
      c[1][i]++;
    else
      c[2][i]++;
  }
  int kk;
  bool flag = 0;
  for (kk = 0; kk < 7 && (!flag); kk++) {
    long long int aa = a[k], bb = b[k], nn = n, mm = m, xx = x;
    nn -= nnmm[kk][0];
    mm -= nnmm[kk][1];
    if (nn < 0 || mm < 0) continue;
    for (i = 0; i < 3; i++)
      if (combi[kk][i] == 1) xx -= c[i][k];
    nn /= 2;
    mm /= 2;
    for (i = 0; i <= nn && (!flag); i++) {
      for (j = 0; j <= mm && (!flag); j++) {
        if (xx == i * aa + j * bb) {
          flag = 1;
          int cnt1 = 0, cnt2 = 0;
          if (combi[kk][0] == 1) {
            str1[n - 1] = 'A';
            str2[0] = 'C';
          }
          if (combi[kk][1] == 1) {
            str1[0] = 'C';
            str2[m - 1] = 'A';
          }
          if (combi[kk][2] == 1) {
            str2[0] = 'C';
            str2[m - 1] = 'A';
          }
          if (str1[n - 1] == 'A') n--;
          if (str1[0] == 'C') cnt1++;
          if (str2[m - 1] == 'A') m--;
          if (str2[0] == 'C') cnt2++;
          while (i != 0) {
            str1[cnt1++] = 'A';
            str1[cnt1++] = 'C';
            i--;
          }
          for (; cnt1 < n; cnt1++) {
            str1[cnt1] = 'B';
          }
          while (j != 0) {
            str2[cnt2++] = 'A';
            str2[cnt2++] = 'C';
            j--;
          }
          for (; cnt2 < m; cnt2++) {
            str2[cnt2] = 'B';
          }
          printf("%s\n%s", str1, str2);
        }
      }
    }
  }
  if (!flag) printf("Happy new year!");
  return 0;
}
