#include <bits/stdc++.h>
using namespace std;
const int maxn = 100 + 10;
int k, x, n, m;
int st1, en1, st2, en2;
long long ac1, ac2;
bool flag;
bool Check(int s1, int s2, int t1, int t2, long long i, long long j) {
  int mx1 = n;
  int mx2 = m;
  if (s1 == 2) mx1--;
  if (t1 == 2) mx2--;
  if (s2 == 1) mx1--;
  if (t2 == 1) mx2--;
  if (s1 == 0) mx1--;
  if (t1 == 0) mx2--;
  if (s2 == 0) mx1--;
  if (t2 == 0) mx2--;
  if (mx1 / 2 < i) return false;
  if (mx2 / 2 < j) return false;
  for (int l = 1; l <= k - 2; l++) {
    long long temp = i + j;
    i = j;
    j = temp;
    if (s2 == 1 && t1 == 2) j++;
    int q1 = s1, q2 = s2;
    s1 = t1;
    s2 = t2;
    t1 = q1;
    t2 = s2;
  }
  if (j == x)
    return true;
  else
    return false;
}
int main() {
  cin >> k >> x >> n >> m;
  for (int s1 = 0; s1 <= 2; s1++) {
    for (int s2 = 0; s2 <= 2; s2++) {
      for (int t1 = 0; t1 <= 2; t1++) {
        for (int t2 = 0; t2 <= 2; t2++) {
          for (long long i = 0; i <= n / 2; i++) {
            for (long long j = 0; j <= m / 2; j++) {
              if (n == 1)
                if (s1 != s2) continue;
              if (m == 1)
                if (t1 != t2) continue;
              if (Check(s1, s2, t1, t2, i, j)) {
                flag = true;
                st1 = s1;
                st2 = t1;
                en1 = s2;
                en2 = t2;
                ac1 = i;
                ac2 = j;
                break;
              }
            }
          }
        }
      }
    }
  }
  if (!flag)
    cout << "Happy new year!";
  else {
    if (st1 == 1) {
      for (int i = 1; i <= ac1; i++) cout << "AC";
      int t = n - (2 * ac1);
      for (int i = 1; i < t; i++) cout << "Z";
      if (t > 0) {
        if (en1 == 0)
          cout << "Z";
        else if (en1 == 1)
          cout << "A";
        else
          cout << "C";
      }
    } else {
      if (st1 == 0)
        cout << "Z";
      else
        cout << "C";
      for (int i = 1; i <= ac1; i++) cout << "AC";
      int t = n - (2 * ac1);
      t--;
      for (int i = 1; i < t; i++) cout << "Z";
      if (t > 0) {
        if (en1 == 0)
          cout << "Z";
        else if (en1 == 1)
          cout << "A";
        else
          cout << "C";
      }
    }
    cout << endl;
    if (st2 == 1) {
      for (int i = 1; i <= ac2; i++) cout << "AC";
      int t = m - (2 * ac2);
      for (int i = 1; i < t; i++) cout << "Z";
      if (t > 0) {
        if (en2 == 0)
          cout << "Z";
        else if (en2 == 1)
          cout << "A";
        else
          cout << "C";
      }
    } else {
      if (st2 == 0)
        cout << "Z";
      else
        cout << "C";
      for (int i = 1; i <= ac2; i++) cout << "AC";
      int t = m - (2 * ac2);
      t--;
      for (int i = 1; i < t; i++) cout << "Z";
      if (t > 0) {
        if (en2 == 0)
          cout << "Z";
        else if (en2 == 1)
          cout << "A";
        else
          cout << "C";
      }
    }
  }
}
