#include <bits/stdc++.h>
using namespace std;
int k, x, n, m, ans1, ans2, k1, k2, k3, k4, yes;
string s1, s2;
void solve2(int sum1, int sum2, vector<int> ok) {
  if (ok[0]) s1 += 'C';
  if (ok[2]) s2 += 'C';
  for (int i = 0; i < sum1; i++) s1 += "AC";
  for (int i = 0; i < sum2; i++) s2 += "AC";
  if (ok[1]) {
    while (s1.length() < n - 1) s1 += 'B';
    s1 += 'A';
  } else {
    while (s1.length() < n) s1 += 'B';
  }
  if (ok[3]) {
    while (s2.length() < m - 1) s2 += 'B';
    s2 += 'A';
  } else {
    while (s2.length() < m) s2 += 'B';
  }
}
void ch(int sum1, int sum2, vector<int> ok) {
  long long last1 = sum2;
  long long last2 = sum1;
  long long temp = last2;
  last2 += last1;
  if (ok[1] && ok[2]) last2++;
  for (int i = 4; i <= k; i++) {
    temp = last1;
    last1 = last2;
    last2 += temp;
    if (i % 2 == 0) {
      if (ok[3] && ok[0]) last2++;
    } else {
      if (ok[2] && ok[3]) last2++;
    }
    if (last2 > x) return;
  }
  if (last2 == x) {
    yes = 1;
    solve2(sum1, sum2, ok);
  }
}
void solve(int id, int sum1, int sum2, vector<int> ok) {
  if (id == 0) {
    for (int i = 0; i <= (n / 2); i++) {
      if (i * 2 <= n - 2) {
        solve(id + 1, i, sum2, ok);
        ok[0] = 1;
        solve(id + 1, i, sum2, ok);
        ok[0] = 0;
        ok[1] = 1;
        solve(id + 1, i, sum2, ok);
        ok[0] = 1;
        solve(id + 1, i, sum2, ok);
        ok[0] = 0, ok[1] = 0;
      } else if (i * 2 == n - 1) {
        solve(id + 1, i, sum2, ok);
        ok[0] = 1;
        solve(id + 1, i, sum2, ok);
        ok[0] = 0;
        ok[1] = 1;
        solve(id + 1, i, sum2, ok);
        ok[1] = 0;
      } else if (i * 2 == n) {
        solve(id + 1, i, sum2, ok);
      }
    }
  }
  if (id == 1) {
    for (int i = 0; i <= (m / 2); i++) {
      if (i * 2 <= m - 2) {
        solve(id + 1, sum1, i, ok);
        ok[2] = 1;
        solve(id + 1, sum1, i, ok);
        ok[2] = 0;
        ok[3] = 1;
        solve(id + 1, sum1, i, ok);
        ok[2] = 1;
        solve(id + 1, sum1, i, ok);
        ok[2] = 0, ok[3] = 0;
      } else if (i * 2 == m - 1) {
        solve(id + 1, sum1, i, ok);
        ok[2] = 1;
        solve(id + 1, sum1, i, ok);
        ok[2] = 0;
        ok[3] = 1;
        solve(id + 1, sum1, i, ok);
        ok[3] = 0;
      } else if (i * 2 == m) {
        solve(id + 1, sum1, i, ok);
      }
    }
  }
  if (id == 2) {
    if (!yes) {
      ch(sum1, sum2, ok);
    }
  }
}
int main() {
  cin >> k >> x >> n >> m;
  vector<int> v;
  v.resize(4);
  for (int i = 0; i < 4; i++) v[i] = 0;
  solve(0, 0, 0, v);
  if (yes) {
    cout << s1 << "\n" << s2 << endl;
  } else {
    cout << "Happy new year!";
  }
}
