#include <bits/stdc++.h>
using namespace std;
template <class T>
inline T sqr(T x) {
  return x * x;
}
const double EPS = 1e-6;
const int INF = 0x3fffffff;
const long long LINF = INF * 1ll * INF;
const double PI = acos(-1.0);
using namespace std;
long long dp[55];
const char mp[3] = {'C', 'A', 'B'};
char A[105], B[105];
void fill(int cnt, char *s, int l) {
  int st;
  if (s[0] == 'A')
    st = 0;
  else
    st = 1;
  int i;
  for (i = st; i < st + 2 * cnt && i < l - 1;) {
    if (i == l - 1) break;
    s[i++] = 'A';
    if (i == l - 1) break;
    s[i++] = 'C';
  }
  for (; i < l - 1; i++) s[i] = 'B';
}
int count(char *s, int l) {
  int ans = 0;
  for (int i = 1; i < l; i++) {
    if (s[i - 1] == 'A' && s[i] == 'C') ans++;
  }
  return ans;
}
bool check(int cntA, int cntB, int A1, int A2, int B1, int B2, int n, int m) {
  if (n == 1 && A1 != A2) return false;
  if (m == 1 && B1 != B2) return false;
  A[0] = mp[A1], A[n - 1] = mp[A2];
  B[0] = mp[B1], B[m - 1] = mp[B2];
  fill(cntA, A, n);
  fill(cntB, B, m);
  if (count(A, n) != cntA) return false;
  if (count(B, m) != cntB) return false;
  cout << A << endl;
  cout << B << endl;
  return true;
}
int main(void) {
  long long k, x, n, m;
  cin >> k >> x >> n >> m;
  for (int i = 0; i <= n / 2; i++) {
    for (int j = 0; j <= m / 2; j++) {
      for (int a1 = 0; a1 < 3; a1++) {
        for (int a2 = 0; a2 < 3; a2++)
          for (int b1 = 0; b1 < 3; b1++)
            for (int b2 = 0; b2 < 3; b2++) {
              dp[1] = i;
              dp[2] = j;
              for (int p = 3; p <= k; p++) {
                dp[p] = dp[p - 1] + dp[p - 2];
                if (p == 3 && a2 == 1 && b1 == 0) {
                  dp[p]++;
                } else if (p != 3 && p % 2 == 1 && b2 == 1 && b1 == 0)
                  dp[p]++;
                else if (p % 2 == 0 && b2 == 1 && a1 == 0)
                  dp[p]++;
              }
              if (dp[k] == x && check(i, j, a1, a2, b1, b2, n, m)) {
                return 0;
              }
            }
      }
    }
  }
  cout << "Happy new year!" << endl;
}
