using System;

public class Hello
{
    public static void Main()
    {
        getAns();
    }
    public static void getAns()
    {
        var ng = 1000000000;
        Console.WriteLine("? {0}", ng);
        var a = int.Parse(Console.ReadLine().Trim());
        if (a == 1) { Console.WriteLine(ng); return; }
        var ok = 1;
        while (ng - ok > 1)
        {
            var mid = ok + (ng - ok) / 2;
            Console.WriteLine("? {0}", mid);
            a = int.Parse(Console.ReadLine().Trim());
            if (a == 1) ok = mid;
            else ng = mid;
        }
        Console.WriteLine("? {0}", ok);
    }
}