#include <bits/stdc++.h>
using namespace std;
int k, x, m, n;
long long start[56], finish[56], occ[56];
char ans[123];
void print(char from, char to, int occ, int len) {
  for (int i = (0), _b = (len - 1); i <= _b; i++) ans[i] = 'B';
  int st = 1;
  if (from == 'A') st = 0;
  for (int i = (0), _b = (occ - 1); i <= _b; i++) {
    ans[st + 2 * i] = 'A';
    ans[st + 2 * i + 1] = 'C';
  }
  ans[0] = from;
  ans[len - 1] = to;
  for (int i = (0), _b = (len - 1); i <= _b; i++) cout << ans[i];
  cout << '\n';
}
int main() {
  ios_base::sync_with_stdio(false);
  cin >> k >> x >> n >> m;
  for (int from_1 = ('A'), _b = ('C'); from_1 <= _b; from_1++)
    for (int to_1 = ('A'), _b = ('C'); to_1 <= _b; to_1++)
      if (n > 1 || from_1 == to_1)
        for (int from_2 = ('A'), _b = ('C'); from_2 <= _b; from_2++)
          for (int to_2 = ('A'), _b = ('C'); to_2 <= _b; to_2++)
            if (m > 1 || from_2 == to_2) {
              int in_1 = n - (from_1 != 'A') - (to_1 != 'C');
              int in_2 = m - (from_2 != 'A') - (to_2 != 'C');
              in_1 /= 2;
              in_2 /= 2;
              for (int occ_1 = (0), _b = (in_1); occ_1 <= _b; occ_1++)
                for (int occ_2 = (0), _b = (in_2); occ_2 <= _b; occ_2++) {
                  start[1] = from_1;
                  finish[1] = to_1;
                  occ[1] = occ_1;
                  start[2] = from_2;
                  finish[2] = to_2;
                  occ[2] = occ_2;
                  for (int i = (3), _b = (k); i <= _b; i++) {
                    start[i] = start[i - 2];
                    finish[i] = finish[i - 1];
                    occ[i] = occ[i - 2] + occ[i - 1] +
                             (finish[i - 2] == 'A' && start[i - 1] == 'C');
                  }
                  if (occ[k] == x) {
                    print(from_1, to_1, occ_1, n);
                    print(from_2, to_2, occ_2, m);
                    return 0;
                  }
                }
            }
  cout << "Happy new year!";
}
