#include <bits/stdc++.h>
using namespace std;
bool pre[55], suf[55];
long long c11[55], c12[55], c21[55], c22[55], a1[55], a2[55];
long long k, x, n, m;
void print(bool s1_a, bool s2_a, bool c_s1, bool c_s2, int v1, int v2) {
  if (c_s1) putchar('C');
  int tmp = v1;
  while (tmp--) printf("AC");
  for (int i = c_s1 + v1 * 2; i < n; i++) {
    if (i == n - 1)
      putchar(s1_a ? 'A' : 'B');
    else
      putchar('B');
  }
  puts("");
  if (c_s2) putchar('C');
  tmp = v2;
  while (tmp--) printf("AC");
  for (int i = c_s2 + v2 * 2; i < m; i++) {
    if (i == m - 1)
      putchar(s2_a ? 'A' : 'B');
    else
      putchar('B');
  }
  puts("");
  exit(0);
}
void calc(bool s1_a, bool s2_a, bool c_s1, bool c_s2) {
  int cnt = x;
  if (s1_a && c_s1) cnt -= c11[k];
  if (s1_a && c_s2) cnt -= c12[k];
  if (s2_a && c_s1) cnt -= c21[k];
  if (s2_a && c_s2) cnt -= c22[k];
  if (cnt < 0) return;
  int l1 = n - s1_a - c_s1;
  int l2 = m - s2_a - c_s2;
  for (int v1 = 0; v1 * 2 <= l1; v1++) {
    long long v2 = (cnt - a1[k] * v1) / a2[k];
    if (a1[k] * v1 + a2[k] * v2 != cnt) continue;
    if (v2 * 2 > l2) continue;
    if (v2 < 0) continue;
    print(s1_a, s2_a, c_s1, c_s2, v1, v2);
  }
}
int main() {
  pre[1] = suf[1] = true;
  a1[1] = a2[2] = 1;
  for (int i = 3; i <= 50; i++) {
    pre[i] = pre[i - 2];
    suf[i] = suf[i - 1];
    c11[i] = c11[i - 2] + c11[i - 1];
    c12[i] = c12[i - 2] + c12[i - 1];
    c21[i] = c21[i - 2] + c21[i - 1];
    c22[i] = c22[i - 2] + c22[i - 1];
    a1[i] = a1[i - 2] + a1[i - 1];
    a2[i] = a2[i - 2] + a2[i - 1];
    if (suf[i - 2]) {
      if (pre[i - 1])
        c11[i]++;
      else
        c12[i]++;
    } else {
      if (pre[i - 1])
        c21[i]++;
      else
        c22[i]++;
    }
  }
  cin >> k >> x >> n >> m;
  for (int i = 0; i < 16; i++) calc(!!(i & 8), !!(i & 4), !!(i & 2), !!(i & 1));
  puts("Happy new year!");
}
