#include <bits/stdc++.h>
using namespace std;
const int maxn = 2e5 + 3;
const int maxm = 1e6 + 3;
const int mod = 1e9 + 7;
const int oo = 1e9 + 5;
const long double pi = 3.141592653589793238462643383279502884;
void input() {
  if (fopen("abc"
            ".inp",
            "r")) {
    freopen(
        "abc"
        ".inp",
        "r", stdin);
    freopen(
        "abc"
        ".out",
        "w", stdout);
  }
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
}
int n, m, k, x;
long long s[109];
char b[109], e[109];
void get_str(char b, char e, int AC, int n) {
  string ans = "";
  int be = 1;
  if (b == 'A') be = 0;
  for (int i = 0; i < n; ++i) ans += 'B';
  for (int i = 0; i < AC; ++i) {
    ans[be + i * 2] = 'A';
    ans[be + i * 2 + 1] = 'C';
  }
  ans[0] = b;
  ans[n - 1] = e;
  cout << ans << "\n";
}
int main() {
  input();
  cin >> k >> x >> n >> m;
  for (char be_1 = 'A'; be_1 <= 'C'; ++be_1) {
    for (char en_1 = 'A'; en_1 <= 'C'; ++en_1) {
      if (n == 1 && be_1 != en_1) continue;
      for (char be_2 = 'A'; be_2 <= 'C'; ++be_2) {
        for (char en_2 = 'A'; en_2 <= 'C'; ++en_2) {
          if (m == 1 && be_2 != en_2) continue;
          int max_nAC = (n - (be_1 != 'A') - (en_1 != 'C')) / 2;
          int max_mAC = (m - (be_2 != 'A') - (en_2 != 'C')) / 2;
          for (int nAC = 0; nAC <= max_nAC; ++nAC) {
            if (n == 2 && !nAC && be_1 == 'A' && en_1 == 'C') continue;
            for (int mAC = 0; mAC <= max_mAC; ++mAC) {
              if (m == 2 && !mAC && be_2 == 'A' && en_2 == 'C') continue;
              b[1] = be_1;
              b[2] = be_2;
              e[1] = en_1;
              e[2] = en_2;
              s[1] = nAC;
              s[2] = mAC;
              for (int i = 3; i <= k; ++i) {
                b[i] = b[i - 2];
                e[i] = e[i - 1];
                s[i] =
                    s[i - 2] + s[i - 1] + (e[i - 2] == 'A' && b[i - 1] == 'C');
              }
              if (s[k] == x) {
                get_str(be_1, en_1, nAC, n);
                get_str(be_2, en_2, mAC, m);
                return 0;
              }
            }
          }
        }
      }
    }
  }
  cout << "Happy new year!";
  return 0;
}
