#include <bits/stdc++.h>
using namespace std;
const int maxn = 55;
struct node {
  int tot, st, ed;
} a[maxn];
int k, x, n, m;
bool willwork(int f0, int f1, int f2, int f3, int f4, int f5) {
  memset(a, 0, sizeof(a));
  a[1].tot = f0, a[1].st = f1, a[1].ed = f2;
  a[2].tot = f3, a[2].st = f4, a[2].ed = f5;
  for (int i = 3; i <= k; i++) {
    a[i].tot = a[i - 2].tot + a[i - 1].tot;
    if (a[i - 2].ed == 1 && a[i - 1].st == 1) ++a[i].tot;
    a[i].st = a[i - 2].st;
    a[i].ed = a[i - 1].ed;
    if (a[i].tot > x) return false;
  }
  return (a[k].tot == x);
}
void write(int len, int sum, int one, int two) {
  string st = "";
  if (one == 1) st.push_back('C');
  for (int i = 0; i < sum; i++) st.push_back('A'), st.push_back('C');
  for (int i = 0; i < len - sum * 2 - one - two; i++) st.push_back('Z');
  if (two == 1) st.push_back('A');
  cout << st << endl;
}
bool check() {
  for (int i = 0; i <= n / 2; i++)
    for (int j = 0; j <= m / 2; j++) {
      int l1 = n - i * 2;
      int l2 = m - j * 2;
      for (int f1 = 0; f1 < 2; f1++)
        for (int f2 = 0; f2 < 2; f2++) {
          if (f1 + f2 > l1) continue;
          for (int f3 = 0; f3 < 2; f3++)
            for (int f4 = 0; f4 < 2; f4++) {
              if (f3 + f4 > l2) continue;
              if (willwork(i, f1, f2, j, f3, f4)) {
                write(n, i, f1, f2);
                write(m, j, f3, f4);
                return true;
              }
            }
        }
    }
  return false;
}
int main() {
  scanf("%d%d%d%d", &k, &x, &n, &m);
  bool temp = check();
  if (temp == false) cout << "Happy new year!" << endl;
  return 0;
}
