#include <bits/stdc++.h>
int k, x, n, m, p;
long long check(int s1c, int s1a, long long s1ac, int s2c, int s2a,
                long long s2ac) {
  if (k == 1) {
    return s1ac;
  }
  if (k == 2) {
    return s2ac;
  }
  long long s3c, s3a, s3ac;
  for (int i = 3; i < (int)k + 1; i++) {
    s3c = s1c;
    s3a = s2a;
    s3ac = s1ac + s2ac + (s1a && s2c);
    s1c = s2c;
    s1a = s2a;
    s1ac = s2ac;
    s2c = s3c;
    s2a = s3a;
    s2ac = s3ac;
  }
  return s3ac;
}
int main() {
  while (scanf("%d%d%d%d", &k, &x, &n, &m) == 4) {
    p = 1;
    for (int s1c = 0; s1c < (int)2; s1c++)
      for (int s1a = 0; s1a < (int)2; s1a++)
        for (int s1ac = 0; s1ac * 2 + s1c + s1a <= n; s1ac++)
          for (int s2c = 0; s2c < (int)2; s2c++)
            for (int s2a = 0; s2a < (int)2; s2a++)
              for (int s2ac = 0; s2ac * 2 + s2c + s2a <= m; s2ac++) {
                if (check(s1c, s1a, s1ac, s2c, s2a, s2ac) == x) {
                  if (s1c) {
                    putchar('C');
                  }
                  for (int i = 0; i < (int)s1ac; i++) {
                    printf("AC");
                  }
                  for (int i = s1c + 2 * s1ac; i + s1a < n; i++) {
                    printf("B");
                  }
                  if (s1a) {
                    printf("A");
                  }
                  puts("");
                  if (s2c) {
                    putchar('C');
                  }
                  for (int i = 0; i < (int)s2ac; i++) {
                    printf("AC");
                  }
                  for (int i = s2c + 2 * s2ac; i + s2a < m; i++) {
                    printf("B");
                  }
                  if (s2a) {
                    printf("A");
                  }
                  puts("");
                  return 0;
                }
              }
    puts("Happy new year!");
  }
  return 0;
}
