public static String buildAPalindrome(String a, String b) {
    String longest = "";
    for (int ai = 0; ai < a.length(); ai++) {
      StringBuilder aBuilder = new StringBuilder();
      for (int aj = ai; aj < a.length(); aj++) {
        aBuilder.append(a.charAt(aj));
        for (int bi = 0; bi < b.length(); bi++) {
          StringBuilder bBuilder = new StringBuilder();
          for (int bj = bi; bj < b.length(); bj++) {
            bBuilder.append(b.charAt(bj));
            String palindrome = aBuilder.toString() + bBuilder.toString();
            if (!palindrome.equals(new StringBuilder(palindrome).reverse().toString())) continue;
            if (
              palindrome.length() > longest.length()
              || (palindrome.length() == longest.length() && palindrome.compareTo(longest) < 0)
            ) {
              longest = palindrome;
            }
          }
        }
      }
    }
    return longest.isEmpty() ? "-1" : longest;
  }