#include <bits/stdc++.h>
using namespace std;
int kk, x, n, m;
string s;
void getans(char c, int l, char c1, char c2, int l1, char c3) {
  string a, b;
  a.resize(n);
  b.resize(m);
  for (int i = 0; i < n; i++) {
    a[i] = 'B';
  }
  for (int i = 0; i < m; i++) {
    b[i] = 'B';
  }
  a[0] = c;
  a[n - 1] = c1;
  b[0] = c2;
  b[m - 1] = c3;
  for (int i = 1; i < n - 1; i++) {
    if (a[i - 1] == 'A' && l > 0 && a[i] == 'B') {
      a[i] = 'C';
      l--;
    }
    if (l > 0 && a[i] == 'B' && a[i + 1] == 'C') {
      a[i] = 'A';
      l--;
    }
    if (a[i] == 'B' && a[i + 1] == 'B' && l > 0) {
      a[i] = 'A';
      a[i + 1] = 'C';
      l--;
    }
  }
  for (int i = 1; i < m - 1; i++) {
    if (b[i - 1] == 'A' && l > 0 && b[i] == 'B') {
      b[i] = 'C';
      l1--;
    }
    if (l > 0 && b[i] == 'B' && b[i + 1] == 'C') {
      b[i] = 'A';
      l1--;
    }
    if (b[i] == 'B' && b[i + 1] == 'B' && l1 > 0) {
      b[i] = 'A';
      b[i + 1] = 'C';
      l1--;
    }
  }
  if (n == 2 && a == "AC") {
    l--;
  }
  if (m == 2 && b == "AC") {
    l1--;
  }
  if (l == 0 && l1 == 0) {
    cout << a << endl;
    cout << b << endl;
    exit(0);
  }
}
int main() {
  cin >> kk >> x >> n >> m;
  s = "ABC";
  for (int i = 0; i < 3; i++) {
    for (int j = 0; j < 3; j++) {
      for (int k = 0; k < 3; k++) {
        for (int g = 0; g < 3; g++) {
          for (int t = 0; t <= n / 2; t++) {
            for (int t1 = 0; t1 <= m / 2; t1++) {
              if (n == 1 && i != j) {
                continue;
              }
              if (m == 1 && k != g) {
                continue;
              }
              if (kk == 1 && x == t) {
                getans(s[i], t, s[j], s[k], t1, s[g]);
              }
              if (kk == 2 && x == t1) {
                getans(s[i], t, s[j], s[k], t1, s[g]);
              }
              int i1 = i, j1 = j, k1 = k, g1 = g;
              long long tt = t, tt1 = t1;
              for (int l = 3; l <= kk; l++) {
                int c = 0;
                if (j1 == 0 && k1 == 2) {
                  c = 1;
                }
                int i2 = i1;
                i1 = k1;
                j1 = g1;
                int tt2 = tt;
                tt = tt1;
                tt1 = tt2 + tt1 + c;
                k1 = i2;
              }
              if (tt1 == x) {
                getans(s[i], t, s[j], s[k], t1, s[g]);
              }
            }
          }
        }
      }
    }
  }
  cout << "Happy new year!" << endl;
  return 0;
}
