#include <bits/stdc++.h>
using namespace std;
int n, m, k, x;
bool calc(long long n1, long long n2, char f1, char l1, char f2, char l2) {
  for (int i = 2; i < k; i++) {
    n2 = n2 + n1;
    n1 = n2 - n1;
    if (l1 == 'A' && f2 == 'C') n2++;
    char f3 = f1;
    char l3 = l2;
    f1 = f2;
    l1 = l2;
    f2 = f3;
    l2 = l3;
    if (n2 > x) return false;
  }
  return n2 == x;
}
int main() {
  ios::sync_with_stdio(false);
  cin >> k >> x >> n >> m;
  char s[] = "ABC";
  for (int i = 0; i < 3; i++)
    for (int j = 0; j < 3; j++)
      for (int k = 0; k < 3; k++)
        for (int h = 0; h < 3; h++) {
          if (n == 1 && i != j) continue;
          if (m == 1 && k != h) continue;
          int en = n, em = m;
          if (s[i] != 'A') en--;
          if (s[j] != 'C') en--;
          if (s[k] != 'A') em--;
          if (s[h] != 'C') em--;
          int mx1 = en / 2;
          int mx2 = em / 2;
          int S1 = 0, S2 = 0;
          if (n == 2 && s[i] == 'A' && s[j] == 'C') S1 = 1;
          if (m == 2 && s[k] == 'A' && s[h] == 'C') S2 = 1;
          for (int N1 = S1; N1 <= mx1; N1++)
            for (int N2 = S1; N2 <= mx2; N2++) {
              if (calc(N1, N2, s[i], s[j], s[k], s[h])) {
                int len = 0;
                if (s[i] != 'A' || N1 == 0) {
                  cout << s[i];
                  len++;
                }
                for (int i = 0; i < N1; i++) {
                  cout << "AC";
                  len += 2;
                }
                while (len + 1 < n) {
                  cout << "B";
                  len++;
                }
                if (len != n) cout << s[j];
                cout << endl;
                len = 0;
                if (s[k] != 'A' || N2 == 0) {
                  cout << s[k];
                  len++;
                }
                for (int i = 0; i < N2; i++) {
                  cout << "AC";
                  len += 2;
                }
                while (len + 1 < m) {
                  cout << "B";
                  len++;
                }
                if (len != m) cout << s[h];
                cout << endl;
                return 0;
              }
            }
        }
  cout << "Happy new year!" << endl;
  return 0;
}
