#include <bits/stdc++.h>
using namespace std;
const int MAXINT = 1 << 31 - 1;
const long long MAXLONG = (long long)1 << 63 - 1;
const int MAXN = 55;
int k, x, n, m;
long long len[MAXN], ac[MAXN], back_a[MAXN], front_c[MAXN];
void printAns(int tot, int f, int bo, int b) {
  if (f) {
    printf("C");
  }
  for (int i = (0); i < (tot - f - bo * 2 - b); i += 1) {
    printf("B");
  }
  for (int i = (0); i < (bo); i += 1) {
    printf("AC");
  }
  if (b) {
    printf("A");
  }
  printf("\n");
}
int main() {
  while (scanf("%d %d %d %d", &k, &x, &n, &m) != -1) {
    bool ok = false;
    for (int i = (0); i < (n / 2 + 1); i += 1) {
      for (int j = (0); j < (m / 2 + 1); j += 1) {
        for (int a1 = (0); a1 < (2); a1 += 1)
          for (int c1 = (0); c1 < (2); c1 += 1)
            for (int a2 = (0); a2 < (2); a2 += 1)
              for (int c2 = (0); c2 < (2); c2 += 1) {
                int len1 = i * 2 + a1 + c1;
                int len2 = j * 2 + a2 + c2;
                if (len1 > n || len2 > m) {
                  continue;
                }
                len[1] = n, front_c[1] = c1, back_a[1] = a1, ac[1] = i;
                len[2] = m, front_c[2] = c2, back_a[2] = a2, ac[2] = j;
                for (int ii = (3); ii < (k + 1); ii += 1) {
                  len[ii] = len[ii - 2] + len[ii - 1];
                  ac[ii] = ac[ii - 2] + ac[ii - 1];
                  if (back_a[ii - 2] && front_c[ii - 1]) {
                    ac[ii]++;
                  }
                  front_c[ii] = front_c[ii - 2];
                  back_a[ii] = back_a[ii - 1];
                  if (ac[ii] > x) {
                    ac[k] = x + 1;
                    break;
                  }
                }
                if (ac[k] == x) {
                  printAns(n, front_c[1], ac[1], back_a[1]);
                  printAns(m, front_c[2], ac[2], back_a[2]);
                  ok = true;
                  goto end;
                }
              }
      }
    }
  end:;
    if (!ok) {
      puts("Happy new year!");
    }
  }
  return 0;
}
