#include <bits/stdc++.h>
using namespace std;
bool check(int k, int x, int n, int m, int i1, int l1, int r1, int i2, int l2,
           int r2) {
  if (i1 * 2 + l1 + r1 > n) return 0;
  if (i2 * 2 + r2 + l2 > m) return 0;
  for (int i = 0; i < k - 2; i++) {
    int l3 = l1;
    int r3 = r2;
    int i3 = i1 + i2 + (r1 * l2);
    l1 = l2;
    r1 = r2;
    i1 = i2;
    l2 = l3;
    r2 = r3;
    i2 = i3;
    if (i2 > x) return 0;
  }
  if (i2 == x) return 1;
  return 0;
}
string build(int n, int p, int l, int r) {
  string s1 = string(n, 'T');
  if (l) s1[0] = 'C';
  if (r) s1[n - 1] = 'A';
  for (int i = 0; i < p; i++) {
    s1[l + 2 * i] = 'A';
    s1[l + 2 * i + 1] = 'C';
  }
  return s1;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int k, x, n, m;
  cin >> k >> x >> n >> m;
  for (int i1 = 0; i1 <= n / 2; i1++) {
    for (int l1 = 0; l1 < 2; l1++) {
      for (int r1 = 0; r1 < 2; r1++) {
        for (int i2 = 0; i2 <= m / 2; i2++) {
          for (int l2 = 0; l2 < 2; l2++) {
            for (int r2 = 0; r2 < 2; r2++) {
              if (check(k, x, n, m, i1, l1, r1, i2, l2, r2)) {
                string s1 = build(n, i1, l1, r1);
                string s2 = build(m, i2, l2, r2);
                cout << s1 << '\n' << s2;
                return 0;
              }
            }
          }
        }
      }
    }
  }
  cout << "Happy new year!";
  return 0;
}
