using System;
using System.Collections.Generic;
using static System.Console;
using System.Linq;

class yuki1
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static void Main()
    {
        var s = ReadLine();
        while (IsPalindrome(s))
        {
            if (s.Length == 1)
            {
                WriteLine(-1);
                return;
            }
            if (s.Length == 2)
            {
                WriteLine(0);
                return;
            }
            s = string.Concat(s.Take(s.Length - 2));
        }
        WriteLine(s.Length);
    }
    static bool IsPalindrome(string s)
    {
        for (var i = 0; i < s.Length / 2; ++i)
        {
            if (s[i] != s[s.Length - i - 1]) return false;
        }
        return true;
    }
}