#include <bits/stdc++.h>
using namespace std;
string generate(int count, int left, int right, int length) {
  string res = "";
  for (int i = 0; i < count; ++i) res += "AC";
  if (left == 0)
    res = "B" + res;
  else if (left == 2)
    res = "C" + res;
  else if (((int)res.size()) > 0 && res.at(0) != 'A')
    res += "A";
  while ((int)res.size() + 1 < length) res += "B";
  if (right == 0)
    res += "B";
  else if (right == 1)
    res += "A";
  else if (((int)res.size()) > 0 && res.at(((int)res.size()) - 1) != 'C')
    res += "C";
  if ((int)res.size() > length) return "";
  return res;
}
long long calculate(long long f1, int l1, int r1, long long f2, int l2, int r2,
                    int k) {
  if (k == 0) return f2;
  long long count = f1 + f2 + (r1 == 1 && l2 == 2);
  return calculate(f2, l2, r2, count, l1, r2, k - 1);
}
int main() {
  ios::sync_with_stdio(false);
  int k, n, m;
  long long x;
  cin >> k >> x >> n >> m;
  for (int i = 0; i < 2 * n; ++i)
    for (int l1 = 0; l1 < 3; ++l1)
      for (int r1 = 0; r1 < 3; ++r1)
        for (int j = 0; j < 2 * m; ++j)
          for (int l2 = 0; l2 < 3; ++l2)
            for (int r2 = 0; r2 < 3; ++r2)
              if (calculate(i, l1, r1, j, l2, r2, k - 2) == x) {
                string s1 = generate(i, l1, r1, n);
                if (s1 == "") continue;
                string s2 = generate(j, l2, r2, m);
                if (s2 == "") continue;
                cout << s1 << endl << s2 << endl;
                return 0;
              }
  cout << "Happy new year!\n";
  return 0;
}
