using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main()
    {
        long answer = 500000000;
        long nowRange = answer / 2;
        long qCount = 100;
        bool flag = false;
        while (nowRange > 0)
        {
            LIB.IO.W("? " + answer.ToString());
            LIB.IO.WFLUSH();
            if (LIB.IO.R<int>() == 1)
            {
                answer += nowRange;
                flag = true;
            }
            else
            {
                answer -= nowRange;
                flag = false;
            }
            nowRange >>= 1;
            qCount--;
        }
        if (flag == true)
        {
            answer += qCount / 2;
        }
        else
        {
            answer -= qCount / 2;
        }
        for (int i = 0; i < qCount; i++)
        {
            LIB.IO.W("? " + answer.ToString());
            LIB.IO.WFLUSH();
            if (LIB.IO.R<int>() == 1)
            {
                answer++;
                if (flag == true) { break; }
            }
            else
            {
                answer--;
                if (flag == false) { break; }
            }
        }
        LIB.IO.W("! " + answer.ToString());
        LIB.IO.WFLUSH();
    }
}

namespace LIB
{
    public class IO
    {
        private const int WMAX = 1000;
        private static string WSTRING = "";
        public static T R<T>()
        {
            return (T)(Convert.ChangeType(R(), typeof(T)));
        }
        public static T[] R<T>(char splitter = ' ')
        {
            return R().Split(splitter).Select(v => UTILITY.PARSE<T>(v)).ToArray();
        }
        public static T[] R<T>(int length)
        {

            T[] ret = new T[length];
            for (int i = 0; i < length; i++)
            {
                ret[i] = R<T>();
            }
            return ret;
        }
        public static T[][] R<T>(int length, char splitter = ' ')
        {
            T[][] ret = new T[length][];
            for (int i = 0; i < length; i++)
            {
                ret[i] = R<T>(splitter);
            }
            return ret;
        }
        private static string R()
        {
            return Console.ReadLine();
        }
        public static void W(object value, bool addLineFeed = true)
        {
            WSTRING += UTILITY.PARSE<string>(value);
            if (addLineFeed == true) { WSTRING += "\n"; }
            if (WSTRING.Count() >= WMAX) { WFLUSH(); }
        }
        public static void WFLUSH()
        {
            Console.Write(WSTRING);
            WSTRING = "";
        }
    }
    public class UTILITY
    {
        public static T PARSE<T>(object value)
        {
            return (T)(Convert.ChangeType(value, typeof(T)));
        }
    }
    public class MEMO<Key, Result>
    {
        private Dictionary<Key, Result> results;
        public MEMO()
        {
            results = new Dictionary<Key, Result>();
        }
        public Result EXEC(Key key, Func<Key, Result> func)
        {
            Result ret = default(Result);
            if (results.ContainsKey(key))
            {
                ret = results[key];
            }
            else
            {
                ret = func(key);
                results.Add(key, ret);
            }
            return ret;
        }
    }
}