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();
        if (!IsPalindrome(s))
        {
            WriteLine(s.Length);
        }
        else if (!IsOneChars(s))
        {
            WriteLine(s.Length - 2);
        }
        else
        {
            WriteLine(0 - (s.Length % 2));
        }
    }
    static bool IsOneChars(string s)
    {
        for (var i = 0; i < s.Length - 1; ++i)
        {
            if (s[i] != s[i + 1]) return false;
        }
        return true;
    }
    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;
    }
}