Minimum Operations to Make a Palindrome

You are given T test cases. For each test case, you are provided with an integer n denoting the length of a string S and the string S itself. Your task is to determine the minimum number of operations required to transform S into a palindrome.

In one operation, you can change any character of the string to any other character. A string S of length n is considered a palindrome if it satisfies the equation $$ S[i] = S[n-i-1] $$ for all $$ 0 \leq i < n $$.

If the string is already a palindrome, the answer is 0.

inputFormat

The input is given via stdin and has the following format:

• The first line contains an integer T, the number of test cases.
• For each test case, the first line contains an integer n, the length of the string.
• The next line contains the string S.

outputFormat

For each test case, output a single integer on a separate line representing the minimum number of operations required to convert the string into a palindrome.

## sample

4
3
abc
4
abba
5
aabaa
6
abccba

1
0
0
0

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