using System;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        string a = Console.ReadLine();
        if (IsPalindrome(a))
            Console.WriteLine("-1");
        else
            for (int i = 0; i < a.Length; i++)
                if (IsPalindrome(a.Remove(i,1)))
                {
                    Console.WriteLine(i);
                    break;
                }
    }

    static bool IsPalindrome(string a)
    {
        for (int i = 0; i < a.Length/2; i++)
        {
            if (a[i] != a[a.Length - 1 - i]) return false;
        }
        return true;
    }
}