int anagram(string s) {
    if(s.size() % 2 == 1) 
        return -1;
    
    int HalfSize = s.size() / 2;
    int count = 0;

    for (int i = 0; i < HalfSize; i++) {
        bool isFound = false;
        for (int j = HalfSize; j < s.size(); j++) {
            if(s[i] == s[j]) {
                s[j] = ' ';  
                isFound = true;
                break;
            }
        }
        
        if (!isFound) 
            count++;  
    }
    
    return count;
}