You are given a string S containing only lowercase characters. 
You can rearrange the string and you have to print minimum number of characters needed(can be 0) to make it palindrome.
-----Input:-----
- First line contain an interger T denoting number of testcases.
- First line of each testcase contains integer N, size of string.
- Second line of each testcase contains string S.
-----Output:-----
For each test case, print a single line containing one integer ― the minimum number of characters needed(can be 0) to make it palindrome.
-----Constraints-----
- $1 \leq T \leq 1000$
- $1 \leq N \leq 10^5$
-----Sample Input:-----
3
1
a
9
abbbcbddd
6
abcdef
-----Sample Output:-----
0
2
5
-----EXPLANATION:-----
- Example case 1: a is already a palindrome.
- Example case 2: abbddcddbba is palindrome by adding 2 more characters.
- Example case 3: abdefcfedba is palindrome by adding 5 more characters.
for _ in range(int(input())):
    n = int(input())
    s = input()
    dic = dict()
    for i in range(n):
        dic[s[i]] = dic.setdefault(s[i], 0) + 1
    ans = 0
    for i in dic:
        if dic[i] % 2 != 0:
            ans += 1
    print(ans - 1 if ans > 0 else ans)

for _ in range(int(input())):
    n = int(input())
    s = input()
    dic = dict()
    for i in range(n):
        dic[s[i]] = dic.setdefault(s[i], 0) + 1
    ans = 0
    for i in dic:
        if dic[i] % 2 != 0:
            ans += 1
    print(ans - 1 if ans > 0 else ans)
