#include <bits/stdc++.h>
using namespace std;
int get(char x, char y, int len) {
  string s;
  s.push_back(x);
  s.push_back(y);
  if (s == "AC") return len / 2;
  if (s == "AA" || s == "CC" || s == "AB" || s == "BC") return (len - 1) / 2;
  return (len - 2) / 2;
}
int a[100], b[100], cnt;
long long c[100][2], d[100][2][2];
int main() {
  int x, cnt, n, m;
  cin >> x >> cnt >> n >> m;
  a[1] = b[1] = 0;
  c[1][0] = 1;
  a[2] = b[2] = 1;
  c[2][1] = 1;
  for (int i = 3; i <= x; i++) {
    a[i] = a[i - 2];
    b[i] = b[i - 1];
    for (int j = 0; j < 2; j++) {
      c[i][j] = c[i - 2][j] + c[i - 1][j];
      for (int k = 0; k < 2; k++) d[i][j][k] = d[i - 2][j][k] + d[i - 1][j][k];
    }
    ++d[i][b[i - 2]][a[i - 1]];
  }
  bool flag = 0;
  char i, j, k, l;
  int u, v;
  for (i = 'A'; i <= 'C'; i++)
    for (j = 'A'; j <= 'C'; j++) {
      if (n == 1) j = i;
      for (k = 'A'; k <= 'C'; k++)
        for (l = 'A'; l <= 'C'; l++) {
          if (m == 1) l = k;
          int N = get(i, j, n), M = get(k, l, m);
          for (u = 0; u <= N; u++)
            for (v = 0; v <= M; v++) {
              long long s = c[x][0] * u + c[x][1] * v +
                            d[x][0][0] * (j == 'A' && i == 'C') +
                            d[x][0][1] * (j == 'A' && k == 'C') +
                            d[x][1][0] * (l == 'A' && i == 'C') +
                            d[x][1][1] * (l == 'A' && k == 'C');
              if (s == cnt) {
                flag = 1;
                goto la;
              }
            }
          if (m == 1) break;
        }
      if (n == 1) break;
    }
la:;
  if (flag) {
    char s[200] = {0}, t[200] = {0};
    s[0] = i;
    s[n - 1] = j;
    t[0] = k;
    t[m - 1] = l;
    int x;
    for (x = i == 'A' ? 0 : 1; u && x < n; x += 2) {
      s[x] = 'A';
      s[x + 1] = 'C';
      --u;
    }
    for (x = !x ? 1 : x; x < n - 1; x++) s[x] = 'B';
    for (x = k == 'A' ? 0 : 1; v && x < m; x += 2) {
      t[x] = 'A';
      t[x + 1] = 'C';
      --v;
    }
    for (x = !x ? 1 : x; x < m - 1; x++) t[x] = 'B';
    puts(s);
    puts(t);
  } else
    puts("Happy new year!");
}
