#include <bits/stdc++.h>
using namespace std;
int k, x, n, m;
long long t[51];
long long f(bool e1, bool e2, bool b1, bool b2, int c1, int c2) {
  t[1] = c1;
  t[2] = c2;
  for (int i = 3; i <= k; ++i) {
    t[i] = t[i - 1] + t[i - 2];
    if (i == 3)
      t[i] += e1 && b2;
    else if (i & 1)
      t[i] += e2 && b2;
    else
      t[i] += e2 && b1;
  }
  return t[k];
}
void o(bool e, bool b, int c, int n) {
  if (b) printf("C");
  for (int i = 0; i < c; ++i) printf("AC");
  for (int i = e + b + 2 * c; i < n; ++i) printf("B");
  if (e) printf("A");
  puts("");
}
int main() {
  scanf("%d %d %d %d", &k, &x, &n, &m);
  for (int e1 = 0; e1 < 2; ++e1)
    for (int e2 = 0; e2 < 2; ++e2)
      for (int b1 = 0; b1 < 2; ++b1)
        for (int b2 = 0; b2 < 2; ++b2)
          for (int c1 = 0; 2 * c1 <= n - e1 - b1; ++c1)
            for (int c2 = 0; 2 * c2 <= m - e2 - b2; ++c2)
              if (f(e1, e2, b1, b2, c1, c2) == x) {
                o(e1, b1, c1, n);
                o(e2, b2, c2, m);
                return 0;
              }
  puts("Happy new year!");
  return 0;
}
