#include <bits/stdc++.h>
using namespace std;
string second = "ACB";
bool check(long long l, long long r, long long k, long long n) {
  if (n == 2 && l == 0 && r == 1 && k == 0) return 0;
  if (n == 1 && l != r) return 0;
  if ((n - (l != 0) - (r != 1)) / 2 < k) return 0;
  return 1;
}
string gen(long long l, long long r, long long k, long long n) {
  string ans;
  ans += second[l];
  for (long long i = 0; i < k; ++i) {
    if (ans.back() == 'A')
      ans += 'C';
    else
      ans += "AC";
  }
  if (ans.size() == n) {
    return ans;
  } else {
    while (ans.size() + 1 < n) ans += 'Z';
    ans += second[r];
    return ans;
  }
}
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  for (long long i = 0; i < 10; ++i) {
    for (long long j = 0; j < 10; ++j) {
      for (long long k = 0; k < 10; ++k) {
        for (long long t = 0; t < 10; ++t) {
          if (check(i, j, k, t)) gen(i, j, k, t);
        }
      }
    }
  }
  long long k, x, n, m;
  cin >> k >> x >> n >> m;
  for (long long l1 = 0; l1 < 3; ++l1) {
    for (long long r1 = 0; r1 < 3; ++r1) {
      for (long long l2 = 0; l2 < 3; ++l2) {
        for (long long r2 = 0; r2 < 3; ++r2) {
          for (long long i = 0; i <= n; ++i) {
            for (long long j = 0; j <= m; ++j) {
              if (check(l1, r1, i, n) && check(l2, r2, j, m)) {
                vector<string> a;
                vector<long long> cnt = {i, j};
                string t;
                t += second[l1];
                t += second[r1];
                a.push_back(t);
                t = "";
                t += second[l2];
                t += second[r2];
                a.push_back(t);
                for (long long t = 3; t <= k; ++t) {
                  cnt.push_back(
                      cnt[cnt.size() - 2] + cnt.back() +
                      (a[a.size() - 2].back() == 'A' && a.back()[0] == 'C'));
                  string lmao;
                  lmao += a[a.size() - 2][0];
                  lmao += a.back().back();
                  a.push_back(lmao);
                }
                if (cnt.back() == x) {
                  cout << gen(l1, r1, i, n) << '\n';
                  cout << gen(l2, r2, j, m) << '\n';
                  exit(0);
                }
              }
            }
          }
        }
      }
    }
  }
  cout << "Happy new year!\n";
}
