#include <bits/stdc++.h>
using namespace std;
int k, x, n, m;
void load() { cin >> k >> x >> n >> m; }
bool bad(int i, int a, int n) {
  int t = i;
  string s = "";
  if (a < 3)
    s += "A";
  else if (a < 6)
    s += "B";
  else
    s += "C";
  for (int j = 1; j < n; j++) {
    s += ".";
    if (s[j - 1] == 'A') {
      s[j] = (i > 0 ? 'C' : 'B');
      if (i > 0) i--;
    } else {
      s[j] = (i > 0 ? 'A' : 'B');
    }
  }
  char qq = '.';
  if (a == 0 || a == 3 || a == 6)
    qq = 'A';
  else if (a == 1 || a == 4 || a == 7)
    qq = 'B';
  else
    qq = 'C';
  if (n == 1 && s[0] != qq) return true;
  s[n - 1] = qq;
  for (int i = 0; i < (int)s.size() - 1; i++) {
    if (s[i] == 'A' && s[i + 1] == 'C') {
      t--;
    }
  }
  return t != 0;
}
int go(int i, int a, int j, int b) {
  for (int q = 0; q < k - 2; q++) {
    int ti = i + j;
    if ((a == 0 || a == 3 || a == 6) && (b >= 6)) ti++;
    int ta = (a / 3) * 3 + b % 3;
    i = j;
    a = b;
    j = ti;
    b = ta;
    if (j > x) return -1;
  }
  return j;
}
void print(int i, int a, int n) {
  cerr << i << " " << a << " " << n << endl;
  string s = "";
  if (a < 3)
    s += "A";
  else if (a < 6)
    s += "B";
  else
    s += "C";
  for (int j = 1; j < n; j++) {
    s += ".";
    if (s[j - 1] == 'A') {
      s[j] = (i > 0 ? 'C' : 'B');
      i--;
    } else {
      s[j] = (i > 0 ? 'A' : 'B');
    }
  }
  if (a == 0 || a == 3 || a == 6)
    s[n - 1] = 'A';
  else if (a == 1 || a == 4 || a == 7)
    s[n - 1] = 'B';
  else
    s[n - 1] = 'C';
  puts(s.c_str());
}
void solve() {
  for (int i = 0; i <= n / 2; i++) {
    for (int j = 0; j <= m / 2; j++) {
      for (int a = 0; a < 9; a++) {
        for (int b = 0; b < 9; b++) {
          if (go(i, a, j, b) == x) {
            if (bad(i, a, n) || bad(j, b, m)) continue;
            print(i, a, n);
            print(j, b, m);
            return;
          }
        }
      }
    }
  }
  puts("Happy new year!");
}
int main() {
  load();
  solve();
  return 0;
}
