package Strings;

import java.util.Scanner;

public class Anagram {
    public static void main(String args[]){
        Scanner sc = new Scanner(System.in);
        //char word[] = {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
        int c;
        int n = sc.nextInt();
        while(n--!=0){
            c=0;
            int count1[] = new int[26];
            int count2[] = new int[26];
            String s = sc.next();
            int l = s.length();
            if(l%2!=0)
                System.out.println(-1);
            else{
            String s1 = s.substring(0,l/2);
            String s2 = s.substring(l/2,l);
            for(int j=0;j<26;j++){
                for(int i=0;i<s1.length();i++){
                    //if(word[j]==s1.charAt(i))
                    if(97+j==s1.charAt(i))
                        count1[j]++;
                }
            }
            for(int j=0;j<26;j++){
                for(int i=0;i<s2.length();i++){
                    //if(word[j]==s2.charAt(i))
                    if(97+j==s2.charAt(i))
                        count2[j]++;
                }
            }
            for(int i=0;i<26;i++){
                c = c + (int)Math.abs(count1[i]-count2[i]);
            }
            System.out.println(c/2);
            }
        }
    }
}