Palindrome_Index

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace _9.Palindrome_Index
{
    class Program
    {
        static void Main(string[] args)
        {
            List<char> str = Console.ReadLine().ToList();
            bool palindromeOrNot = isItAPalindrome(str);

            if (palindromeOrNot)
            {
                Console.WriteLine("-1");
            }
            else
            {
                for (int ch = 0; ch < str.Count; ch++)
                {
                    char oldStr = str[ch];
                    str.RemoveAt(ch);
                    palindromeOrNot = isItAPalindrome(str);
                    if (palindromeOrNot)
                    {
                        Console.WriteLine(ch);
                        break;
                    }
                    str.Insert(ch, oldStr);
                }
            }
        }

        private static bool isItAPalindrome(List<char> str)
        {
            int rightIndex = str.Count - 1;
            int leftIndex = 0;
            while (rightIndex >= leftIndex)
            {
                if (str[rightIndex] != str[leftIndex])
                {
                    return false;
                }
                rightIndex--;
                leftIndex++;
            }
            return true;
        }// end of isItAPalindrome
    }
}