using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

class Program
{
    public void Proc()
    {
        long ans = this.GetAns(1, 1000000000);
        Console.WriteLine("! " + ans);


    }

    private long GetAns(long min, long max)
    {
        long mid = (min + max) / 2;
        Console.WriteLine("? " + mid);
        bool isBigger = Console.ReadLine().Equals("1");

        if (isBigger && max - mid <= 1)
        {
            Console.WriteLine("? " + max);
            isBigger = Console.ReadLine().Equals("1");
            if (isBigger)
            {
                return max;
            }
            else
            {
                return mid;
            }
        }
        if (isBigger)
        {
            return this.GetAns(mid, max);
        }
        else
        {
            return this.GetAns(min, mid);
        }
    }




    static void Main(string[] args)
    {
        Program prg = new Program();
        prg.Proc();
    }
}