using System;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        int chkHani = 0;
        int ansHaniMin = 0;
        int ansHaniMax = (int)Math.Pow(10, 9);

        do
        {
            chkHani = (ansHaniMax - ansHaniMin) / 2 + ansHaniMin;
            Console.WriteLine("? {0}", chkHani);

            if (int.Parse(Console.ReadLine()) == 1) { ansHaniMin = chkHani; }
            else { ansHaniMax = chkHani; }

            if (ansHaniMax - ansHaniMin == 1) { ansHaniMax = ansHaniMin; }

        } while (ansHaniMin != ansHaniMax);

        Console.WriteLine("! {0}", ansHaniMin);
    }
}