#include <bits/stdc++.h>
using namespace std;
const int N = 51;
int k, x, n, m;
long long a[N], b[N], aa[N], ab[N], ba[N], bb[N];
int L[N], R[N];
void pre() {
  L[1] = R[1] = 0;
  L[2] = R[2] = 1;
  a[1] = 1;
  b[2] = 1;
  for (int i = 3; i <= 50; i++) {
    a[i] = a[i - 2] + a[i - 1];
    b[i] = b[i - 2] + b[i - 1];
    aa[i] = aa[i - 2] + aa[i - 1];
    ab[i] = ab[i - 2] + ab[i - 1];
    ba[i] = ba[i - 2] + ba[i - 1];
    bb[i] = bb[i - 2] + bb[i - 1];
    L[i] = L[i - 2];
    R[i] = R[i - 1];
    if (R[i - 2] == 0 && L[i - 1] == 0)
      aa[i]++;
    else if (R[i - 2] == 0 && L[i - 1] == 1)
      ab[i]++;
    else if (R[i - 2] == 1 && L[i - 1] == 0)
      ba[i]++;
    else if (R[i - 2] == 1 && L[i - 1] == 1)
      bb[i]++;
  }
}
int main() {
  pre();
  cin >> k >> x >> n >> m;
  for (int pp = 0; pp <= 1; pp++)
    for (int pk = 0; pk <= 1; pk++)
      for (int kp = 0; kp <= 1; kp++)
        for (int kk = 0; kk <= 1; kk++)
          for (int i = 0; 2 * i + pp + pk <= n; i++)
            for (int j = 0; 2 * j + kp + kk <= m; j++) {
              long long tot = 0;
              tot += a[k] * i;
              tot += b[k] * j;
              tot += aa[k] * (pp && pk);
              tot += ab[k] * (pk && kp);
              tot += ba[k] * (kk && pp);
              tot += bb[k] * (kp && kk);
              if (tot == x) {
                if (pp) printf("C");
                for (int c = 0; c < i; c++) printf("AC");
                for (int c = 0; 2 * i + pp + pk + c < n; c++) printf("B");
                if (pk) printf("A");
                puts("");
                if (kp) printf("C");
                for (int c = 0; c < j; c++) printf("AC");
                for (int c = 0; 2 * j + kp + kk + c < m; c++) printf("B");
                if (kk) printf("A");
                puts("");
                return 0;
              }
            }
  puts("Happy new year!");
  return 0;
}
