using System;
using System.Linq;
class C
{
    static void Main()
    {
        string i = Console.ReadLine();

        int k = i.Distinct().Count();

        if (k != 1)
        {
            int x = 0;
            int o = i.Select(c => i.Remove(x++, 1)).Any(s => s.Reverse().SequenceEqual(s)) ? x : 0;
            Console.WriteLine(x - 1);
        }
        else
        {
            Console.WriteLine(-1);
        }
    }
}