#include <bits/stdc++.h>
using namespace std;
long long count(int k, long long ac, long long bc, bool as, bool ae, bool bs,
                bool be) {
  if (k == 2) return bc;
  int f = 0;
  if (ae == true && bs == true) f++;
  return count(k - 1, bc, ac + bc + f, bs, be, as, be);
}
int k, x, n, m;
string make(int n, int c, bool s, bool e) {
  string r;
  r.resize(n);
  int i = 0;
  if (s) r[i++] = 'C';
  if (e) r[--n] = 'A';
  while (c--) r[i++] = 'A', r[i++] = 'C';
  while (i < n) r[i++] = 'X';
  return r;
}
void test(long long ac, long long bc, bool as, bool ae, bool bs, bool be) {
  if (2 * ac + as + ae > n) return;
  if (2 * bc + bs + be > m) return;
  if (count(k, ac, bc, as, ae, bs, be) == x) {
    cout << make(n, ac, as, ae) << '\n' << make(m, bc, bs, be) << '\n';
    exit(0);
  }
}
int main() {
  cin >> k >> x >> n >> m;
  for (int i = 0; 2 * i <= n; ++i) {
    for (int j = 0; 2 * j <= m; ++j) {
      for (int a = 0; a < 16; ++a) {
        test(i, j, a & 1, 1 & (a >> 1), 1 & (a >> 2), 1 & (a >> 3));
      }
    }
  }
  cout << "Happy new year!\n";
}
