def anagram(s):
    if (len(s) % 2 != 0):
        return -1
    else:
        lst = list(s[len(s)//2:])
        
        for i in s[:len(s)//2]:
            if (i in lst):
                lst.remove(i)
        
        return len(lst)

q = int(input())
for j in range(q):
    s = input()
    
    result = anagram(s)
    
    print(result)