#include <bits/stdc++.h>
using namespace std;
template <class T>
typename T::value_type arr_sum(const T& v, int n) {
  typename T::value_type sum = 0;
  for (int i = (0); i < (n); ++i) sum += v[i];
  return sum;
}
struct Sync_stdio {
  Sync_stdio() {
    cin.tie(NULL);
    ios_base::sync_with_stdio(false);
  }
} _sync_stdio;
int xx, yy, n, m;
char ff1, ll1, ff2, ll2;
void print() {
  string s1(n, 'B');
  string s2(m, 'B');
  int t1 = 1, t2 = 1;
  if (ff1 == 'A') {
    t1 = 0;
  }
  if (ff2 == 'A') {
    t2 = 0;
  }
  s2[0] = ff1;
  s2[m - 1] = ll1;
  s1[0] = ff2;
  s1[n - 1] = ll2;
  for (int i = (0); i < (yy); ++i) {
    s2[t1 + 2 * i] = 'A';
    s2[t1 + 1 + 2 * i] = 'C';
  }
  for (int i = (0); i < (xx); ++i) {
    s1[t2 + 2 * i] = 'A';
    s1[t2 + 1 + 2 * i] = 'C';
  }
  cout << s1 << "\n" << s2 << "\n";
  exit(0);
}
void fib(long long x, int k, long long ac1, long long ac2, char f1, char l1,
         char f2, char l2) {
  if (ac1 == x && k == 0) {
    print();
  }
  if (k == 0 || ac1 >= 2000000000) {
    return;
  }
  long long newac = ac1 + ac2;
  if (l2 == 'A' && f1 == 'C') {
    ++newac;
  }
  fib(x, k - 1, newac, ac1, f2, l1, f1, l1);
}
int check(int n, int m, int i, int j, char i1, char i2, char i3, char i4) {
  if (m == 1 && i1 != i2) {
    return 0;
  }
  if (n == 1 && i3 != i4) {
    return 0;
  }
  int t1 = 0;
  int t2 = 0;
  int u1 = m;
  int u2 = n;
  if (i1 != 'A') {
    ++t1;
  }
  if (i3 != 'A') {
    ++t2;
  }
  if (i2 != 'C') {
    --u1;
  }
  if (i4 != 'C') {
    --u2;
  }
  if ((u2 - t2) / 2 < i) {
    return 0;
  }
  if ((u1 - t1) / 2 < j) {
    return 0;
  }
  return 1;
}
int main() {
  int k, x;
  cin >> k >> x >> n >> m;
  for (int i = (0); i < (n / 2 + 1); ++i) {
    for (int j = (0); j < (m / 2 + 1); ++j) {
      for (int i1 = ('A'); i1 < ('D'); ++i1) {
        for (int i2 = ('A'); i2 < ('D'); ++i2) {
          for (int i3 = ('A'); i3 < ('D'); ++i3) {
            for (int i4 = ('A'); i4 < ('D'); ++i4) {
              if (check(n, m, i, j, i1, i2, i3, i4)) {
                xx = i;
                yy = j;
                ff1 = i1;
                ll1 = i2;
                ff2 = i3;
                ll2 = i4;
                fib(x, k - 2, j, i, i1, i2, i3, i4);
              }
            }
          }
        }
      }
    }
  }
  cout << "Happy new year!";
}
