#include <bits/stdc++.h>
using namespace std;
char a[110];
char b[110];
int main() {
  int k, x, n, m;
  scanf("%d%d%d%d", &k, &x, &n, &m);
  int flag = 0;
  for (int i1 = 0; i1 <= n / 2; i1++)
    for (int i2 = 0; i2 <= m / 2; i2++)
      for (int ab = 0; ab <= 1; ab++)
        for (int bb = 0; bb <= 1; bb++)
          for (int ba = 0; ba <= 1; ba++) {
            if (ab == 1 && ba == 1 && bb == 0) continue;
            long long sum1 = i1, sum2 = i2, sum3 = i1 + i2 + ab;
            int sign = 0;
            for (int j = 4; j <= k; j++) {
              sum1 = sum2;
              sum2 = sum3;
              sum3 = sum1 + sum2 + (j % 2 == 0 ? ba : bb);
              if (sum3 > x) {
                sign = 1;
                break;
              }
            }
            if (sign == 1) continue;
            if (sum3 != x) continue;
            int tn = n, tm = m;
            memset(a, 0, sizeof(a));
            memset(b, 0, sizeof(b));
            if (bb == 1) {
              if (m == 1) continue;
              b[0] = 'C';
              b[m - 1] = 'A';
              tm -= 2;
            }
            if ((ab == 1 && ba == 1) && (n == 1 || m == 1)) continue;
            if (ab == 1) {
              if (b[0] == 0) {
                b[0] = 'C';
                tm--;
              }
              a[n - 1] = 'A';
              tn--;
            }
            if (ba == 1) {
              if (b[m - 1] == 0) {
                b[m - 1] = 'A';
                tm--;
              }
              a[0] = 'C';
              tn--;
            }
            if (tn >= 2 * i1 && tm >= 2 * i2) {
              flag = 1;
              int cnt = 0;
              for (int i = 0; i < n; i++) {
                if (a[i] != 0)
                  printf("%c", a[i]);
                else {
                  if (cnt < i1) {
                    printf("AC");
                    i++;
                    cnt++;
                  } else {
                    printf("B");
                  }
                }
              }
              printf("\n");
              cnt = 0;
              for (int i = 0; i < m; i++) {
                if (b[i] != 0)
                  printf("%c", b[i]);
                else {
                  if (cnt < i2) {
                    printf("AC");
                    i++;
                    cnt++;
                  } else
                    printf("B");
                }
              }
              printf("\n");
              return 0;
            }
          }
  if (flag == 0) printf("Happy new year!\n");
  return 0;
}
