public static int anagram(String s) {
        if (s.length() % 2 != 0) return -1; // If length is odd, return -1

        int[] frequency = new int[26]; // Array for character frequencies

        int mid = s.length() / 2;
        for (int i = 0; i < mid; i++) {
            frequency[s.charAt(i) - 'a']++;  // Count chars in first half
            frequency[s.charAt(i + mid) - 'a']--; // Subtract chars in second half
        }

        int changes = 0;
        for (int count : frequency) {
            if (count > 0) changes += count; // Count excess chars that need replacement
        }

        return changes;
    }