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.

```python

USER_FILENAME = "<user_code>"
import sys, json, builtins
import math, heapq, bisect, itertools, functools, collections, statistics, fractions, decimal, operator, array, random, re, string, os, pathlib
try:
    import resource as _res
except Exception:
    _res = None
from collections import Counter, defaultdict, deque, OrderedDict
from functools import lru_cache, reduce
from itertools import accumulate, permutations, combinations, product
from math import gcd, ceil, floor, sqrt
from decimal import Decimal
try:
    from typing import *
except Exception:
    pass
try:
    sys.setrecursionlimit(1_000_000)
except Exception:
    pass
try:
    import site as _site
    try:
        _sys_sites = _site.getsitepackages() if hasattr(_site, "getsitepackages") else []
        for _p in _sys_sites:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
    try:
        _usp = _site.getusersitepackages()
        if isinstance(_usp, str):
            _usp = [_usp]
        for _p in _usp:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
except Exception:
    pass

ns = {"__name__": "__main__"}
for _k, _v in list(globals().items()):
    if not _k.startswith("_"):
        ns[_k] = _v
_CODE = 'from sys import stdin, stdout\nfrom math import floor, gcd, fabs, factorial, fmod, sqrt, inf, log\nfrom collections import defaultdict as dd, deque\nfrom heapq import merge, heapify, heappop, heappush, nsmallest\nfrom bisect import bisect_left as bl, bisect_right as br, bisect\nmod = pow(10, 9) + 7\nmod2 = 998244353\ndef inp(): return stdin.readline().strip()\ndef out(var, end="\\n"): stdout.write(str(var)+"\\n")\ndef outa(*var, end="\\n"): stdout.write(\' \'.join(map(str, var)) + end)\ndef lmp(): return list(mp())\ndef mp(): return map(int, inp().split())\ndef smp(): return map(str, inp().split())\ndef l1d(n, val=0): return [val for i in range(n)]\ndef l2d(n, m, val=0): return [l1d(n, val) for j in range(m)]\ndef remadd(x, y): return 1 if x%y else 0\ndef ceil(a,b): return (a+b-1)//b\n\ndef isprime(x):\n    if x<=1: return False\n    if x in (2, 3): return True\n    if x%2 == 0: return False\n    for i in range(3, int(sqrt(x))+1, 2):\n        if x%i == 0: return False\n    return True\n\nfor _ in range(int(inp())):\n    n = int(inp())\n    s = inp()\n    md = {}\n    for i in s:\n        if i in md: md[i]+=1\n        else: md[i]=1\n    o, e = 0, 0\n    for i in md.values():\n        if i%2: o+=1\n        else: e+=1\n    print(max(o-1, 0))'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

```

Measured memory_bytes: 16007