#include <bits/stdc++.h>
using namespace std;
bool ok;
long long k, x, n, m;
long long ansa, ansb, ansc, ansd, anse;
long long f1[57];
long long f2[57];
long long f3[57];
long long f4[57];
long long f5[57];
void gao(long long a[], long long k, long long z) {
  for (int i = 4; i <= 50; i++) {
    a[i] = a[i - 1] + a[i - 2];
    if (i % 2 == k) {
      a[i] += z;
    }
  }
}
void init() {
  f1[1] = 1, f1[3] = 1, gao(f1, 0, 0);
  f2[2] = 1, f2[3] = 1, gao(f2, 0, 0);
  f3[3] = 1, gao(f3, 0, 0);
  gao(f4, 1, 1);
  gao(f5, 0, 1);
  ok = false;
}
void cal(long long a, long long b, long long c, long long n, long long m) {
  if (a < 0 || b < 0 || c < 0 || n < 0 || m < 0) return;
  if (ok) return;
  long long cnt1 = n / 2;
  long long cnt2 = m / 2;
  long long res = 0;
  if (a) {
    res += f5[k];
  }
  if (b) {
    res += f4[k];
  }
  if (c) {
    res += f3[k];
  }
  for (int i = 0; i <= cnt1; i++) {
    for (int j = 0; j <= cnt2; j++) {
      if (res + i * f1[k] + j * f2[k] == x) {
        ok = true;
        ansa = a;
        ansb = b;
        ansc = c;
        ansd = i;
        anse = j;
      }
    }
  }
}
int main() {
  init();
  scanf("%lld%lld%lld%lld", &k, &x, &n, &m);
  cal(1, 1, 1, n - 2, m - 2);
  cal(0, 1, 1, n - 1, m - 2);
  cal(1, 1, 0, n - 1, m - 2);
  cal(0, 0, 1, n - 1, m - 1);
  cal(0, 1, 0, n, m - 2);
  cal(1, 0, 0, n - 1, m - 1);
  cal(0, 0, 0, n, m);
  string s, t;
  bool hs = false, fs = false, ht = false, ft = false;
  if (ok == false) {
    printf("Happy new year!\n");
  } else {
    if (ansa) {
      ft = true;
      hs = true;
    }
    if (ansb) {
      ft = true;
      ht = true;
    }
    if (ansc) {
      fs = true;
      ht = true;
    }
    if (hs) {
      s += "C";
    }
    if (ht) {
      t += "C";
    }
    for (int i = 1; i <= ansd; i++) {
      s += "AC";
    }
    for (int i = 1; i <= anse; i++) {
      t += "AC";
    }
    while (s.size() < n) {
      s += 'Z';
    }
    while (t.size() < m) {
      t += 'Z';
    }
    if (ft) {
      t[m - 1] = 'A';
    }
    if (fs) {
      s[n - 1] = 'A';
    }
    cout << s << "\n";
    cout << t << "\n";
  }
}
