Anagram - add all the difference between two strings, and then divide it by 2

Anagram3.cs

using System;
using System.Collections.Generic;
using System.IO;
class Solution {
    static int Solve(string s)
    {
        if(s.Length % 2 == 1)
            return -1;
        int [] count =  new int[26];
        for(int i = 0; i < s.Length /2; ++i)
        {
            count[(int)s[i] - (int)'a'] += 1;
            count[(int)s[s.Length -1 - i] - (int)'a'] -= 1;
        }
        int res = 0;
        foreach(int i in count)
        {
            res += Math.Abs(i);
        }
        return res/2;
    }
    static void Main(String[] args) {
        int t  = Convert.ToInt32(Console.ReadLine());
        for(int i  = 0; i< t; ++i)
        {
            Console.WriteLine(Solve(Console.ReadLine()));
        }
    }
}