#include <bits/stdc++.h>
using namespace std;
const int N = 1000010;
const int mod = 1e9 + 7;
int tms, x, n, m;
string ans1, ans2;
bool cal(int i, int j, long long k, int ii, int jj, long long kk) {
  if (tms == 1) return k;
  if (tms == 2) return kk;
  for (int iter = 3; iter <= tms; ++iter) {
    int add = (j && ii);
    int ti = i, tj = j;
    long long tk = k;
    i = ii, j = jj, k = kk;
    ii = ti, kk += tk + add;
  }
  return kk == x;
}
bool check(int fst, int lst, int num, int len, string &ans) {
  ans = "";
  if (fst) ans += 'C';
  for (int i = 0; i < num; ++i) ans += "AC";
  while (ans.length() < len - lst) ans += 'B';
  if (lst) ans += 'A';
  return ans.length() == len;
}
int main() {
  scanf("%d %d %d %d", &tms, &x, &n, &m);
  for (int i = 0; i < 2; ++i)
    for (int j = 0; j < 2; ++j)
      for (int k = 0; k <= n / 2; ++k) {
        if (!check(i, j, k, n, ans1)) continue;
        for (int ii = 0; ii < 2; ++ii)
          for (int jj = 0; jj < 2; ++jj)
            for (int kk = 0; kk <= m / 2; ++kk) {
              if (!check(ii, jj, kk, m, ans2)) continue;
              if (cal(i, j, k, ii, jj, kk)) {
                cout << ans1 << endl << ans2 << endl;
                exit(0);
              }
            }
      }
  puts("Happy new year!");
  return 0;
}
