#include <bits/stdc++.h>
using namespace std;
const int INF = 1000000000;
char first[51], last[51];
long long AC[51];
char s[3][101], l[3];
int main() {
  int k, x;
  scanf("%d%d", &k, &x);
  int n, m;
  scanf("%d%d", &n, &m);
  int i, j;
  l[1] = n;
  l[2] = m;
  for (first[1] = ('A'); first[1] <= ('C'); first[1]++)
    for (last[1] = ('A'); last[1] <= ('C'); last[1]++) {
      if (n == 1 && first[1] != last[1]) continue;
      for (AC[1] = (0); AC[1] <= (n / 2); AC[1]++) {
        if (n == 2 && AC[1] == 0 && first[1] == 'A' && last[1] == 'C') continue;
        if (AC[1] * 2 == n && (first[1] != 'A' || last[1] != 'C')) continue;
        if (n > 1 && AC[1] * 2 == n - 1 && first[1] != 'A' && last[1] != 'C')
          continue;
        for (first[2] = ('A'); first[2] <= ('C'); first[2]++)
          for (last[2] = ('A'); last[2] <= ('C'); last[2]++) {
            if (m == 1 && first[2] != last[2]) continue;
            for (AC[2] = (0); AC[2] <= (m / 2); AC[2]++) {
              if (m == 2 && AC[2] == 0 && first[2] == 'A' && last[2] == 'C')
                continue;
              if (AC[2] * 2 == m && (first[2] != 'A' || last[2] != 'C'))
                continue;
              if (m > 1 && AC[2] * 2 == m - 1 && first[2] != 'A' &&
                  last[2] != 'C')
                continue;
              for (i = (3); i <= (k); i++) {
                first[i] = first[i - 2];
                last[i] = last[i - 1];
                AC[i] = AC[i - 2] + AC[i - 1];
                if (last[i - 2] == 'A' && first[i - 1] == 'C') AC[i]++;
              }
              if (AC[k] != x) continue;
              for (j = (1); j <= (2); j++) {
                fill(s[j], s[j] + l[j], 'B');
                s[j][0] = first[j];
                s[j][l[j] - 1] = last[j];
                if (s[j][0] == 'A')
                  for (i = 0; i < (2 * AC[j]); i++)
                    s[j][i] = (i % 2) ? 'C' : 'A';
                else
                  for (i = (1); i <= (2 * AC[j]); i++)
                    s[j][i] = (i % 2) ? 'A' : 'C';
                puts(s[j]);
              }
              return 0;
            }
          }
      }
    }
  puts("Happy new year!");
  return 0;
}
