#include <bits/stdc++.h>
using namespace std;
long long f[56];
int main(void) {
  int k, x, n, m, t;
  scanf("%d%d%d%d", &k, &x, &n, &m);
  for (int i = 0; i <= n >> 1; i++)
    for (int j = 0; j <= m >> 1; j++) {
      for (int a = 0; a <= 1; a++)
        for (int b = 0; b <= 1; b++)
          for (int c = 0; c <= 1; c++)
            for (int d = 0; d <= 1; d++) {
              if (i * 2 + a + b > n || j * 2 + c + d > m) continue;
              f[1] = i;
              f[2] = j;
              t = 0;
              if (b != 0 && c != 0) t++;
              for (int z = 3; z <= k; z++) {
                f[z] = f[z - 1] + f[z - 2];
                if (t != 0) {
                  f[z]++;
                  t--;
                }
                if (z > 3 && d != 0 && a != 0 && z % 2 == 0) ++f[z];
                if (z > 3 && d != 0 && c != 0 && z % 2 == 1) ++f[z];
              }
              if (f[k] == x) {
                if (a != 0) cout << "C";
                for (int z = 0; z <= i - 1; z++) cout << "AC";
                for (int z = 0; z <= n - i * 2 - a - b - 1; z++) cout << "Z";
                if (b != 0) cout << "A";
                cout << endl;
                if (c != 0) cout << "C";
                for (int z = 0; z <= j - 1; z++) cout << "AC";
                for (int z = 0; z <= m - j * 2 - c - d - 1; z++) cout << "Z";
                if (d != 0) cout << "A";
                cout << endl;
                return 0;
              }
            }
    }
  cout << "Happy new year!" << endl;
  return 0;
}
