#include <bits/stdc++.h>
using namespace std;
long long n, m, E[80], F[80], q, nr12, nr22, nr1, k, t, nr21, nr2, N, M, cap1,
    cap2, S, x, i, j, OK, t1, t2, e1, e2;
char s1[300], s2[300];
int back(long long n12, long long n21, long long n22) {
  N = n;
  M = m;
  if (n12 && n21 && n22) {
    N -= 2;
    M -= 2;
  } else if (n12 && n21) {
    N -= 2;
    M -= 2;
  } else if (n21 && n22) {
    M -= 2;
    N--;
  } else if (n22 && n12) {
    N--;
    M -= 2;
  } else if (n12) {
    N--;
    M--;
  } else if (n21) {
    N--;
    M--;
  } else if (n22) {
    M -= 2;
  }
  if (N < 0 || M < 0) return 0;
  cap1 = N / 2;
  cap2 = M / 2;
  S = x;
  S = S - n21 - n22 - n12;
  if (S < 0) return 0;
  for (i = 0; i <= cap1; ++i) {
    for (j = 0; j <= cap2; ++j)
      if (1LL * (1LL * i * nr1 + 1LL * j * nr2) == S) {
        OK = 1;
        break;
      }
    if (OK) break;
  }
  if (OK) {
    t1 = t2 = 1;
    e1 = n;
    e2 = m;
    if (n12) {
      s1[n] = 'A';
      s2[1] = 'C';
    }
    if (n21) {
      s2[m] = 'A';
      s1[1] = 'C';
    }
    if (n22) {
      s2[1] = 'C';
      s2[m] = 'A';
    }
    if (s1[1]) t1++;
    if (s2[1]) t2++;
    if (s1[n]) e1--;
    if (s2[m]) e2--;
    for (t = t1; i && t <= e1; t += 2, --i) {
      s1[t] = 'A';
      s1[t + 1] = 'C';
    }
    for (q = t2; j && q <= e2; q += 2, --j) {
      s2[q] = 'A';
      s2[q + 1] = 'C';
    }
    for (; t <= e1; t++) s1[t] = 'X';
    for (; q <= e2; q++) s2[q] = 'X';
    cout << (s1 + 1) << "\n" << (s2 + 1);
    return 1;
  }
  return 0;
}
int main() {
  cin >> k >> x >> n >> m;
  F[1] = F[2] = 1;
  for (i = 3; i <= k; ++i) F[i] = F[i - 1] + F[i - 2];
  nr1 = F[k - 2];
  nr2 = F[k - 1];
  nr12 = F[k - 2];
  E[4] = 1;
  for (i = 5; i <= k; ++i) {
    if (i & 1)
      E[i] = E[i - 1] + E[i - 2];
    else
      E[i] = E[i - 1] + E[i - 2] + 1;
  }
  nr21 = E[k];
  nr22 = E[k - 1];
  if (back(nr12, nr21, nr22)) return 0;
  if (back(nr12, 0, 0)) return 0;
  if (back(0, nr21, 0)) return 0;
  if (back(0, 0, nr22)) return 0;
  if (back(nr12, nr21, 0)) return 0;
  if (back(nr12, 0, nr22)) return 0;
  if (back(0, nr21, nr22)) return 0;
  if (back(0, 0, 0)) return 0;
  cout << "Happy new year!";
  return 0;
}
