#include <bits/stdc++.h>
using namespace std;
bool test(long long k, long long x, long long n, long long m, long long p1,
          long long l1, long long r1, long long p2, long long l2,
          long long r2) {
  if (p1 * 2 + l1 + r1 > n) return false;
  if (p2 * 2 + l2 + r2 > m) return false;
  for (long long i = 0; i < k - 2; i++) {
    long long p3 = p1 + p2 + (r1 * l2);
    long long l3 = l1;
    long long r3 = r2;
    l1 = l2;
    r1 = r2;
    p1 = p2;
    l2 = l3;
    r2 = r3;
    p2 = p3;
    if (p2 > x) return false;
  }
  return p2 == x;
}
string build(long long n, long long p, long long l, long long r) {
  string s(n, 'X');
  if (l) s[0] = 'C';
  if (r) s[n - 1] = 'A';
  for (long long i = 0; i < p; i++) {
    s[l + i * 2] = 'A';
    s[l + i * 2 + 1] = 'C';
  }
  return s;
}
signed main() {
  ios::sync_with_stdio(false);
  long long k, x, n, m;
  cin >> k >> x >> n >> m;
  for (long long p1 = 0; p1 <= n / 2; p1++) {
    for (long long l1 = 0; l1 <= 1; l1++) {
      for (long long r1 = 0; r1 <= 1; r1++) {
        for (long long p2 = 0; p2 <= m / 2; p2++) {
          for (long long l2 = 0; l2 <= 1; l2++) {
            for (long long r2 = 0; r2 <= 1; r2++) {
              if (test(k, x, n, m, p1, l1, r1, p2, l2, r2)) {
                string s1 = build(n, p1, l1, r1);
                string s2 = build(m, p2, l2, r2);
                cout << s1 << "\n" << s2 << "\n";
                return 0;
              }
            }
          }
        }
      }
    }
  }
  cout << "Happy new year!\n";
  return 0;
}
