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

namespace ProgrammingContest
{
    class MainClass : IDisposable
    {
        Scanner sc;
        Writer wr;
        string backPath = "..";
        char dirSep = System.IO.Path.DirectorySeparatorChar;
        string inFilePath = null;
        string outFilePath = null;
        public MainClass()
        {
            this.inFilePath = this.backPath
                            + this.dirSep
                            + this.backPath
                            + this.dirSep
                            + "in.txt";
            this.outFilePath = this.backPath
                             + this.dirSep
                             + this.backPath
                             + this.dirSep
                             + "out.txt";
        }
        static void Main(string[] args)
        {
            //var hoge = new ProgrammingContestHoge.Hoge();
            using (var mainClass = new MainClass())
            {
                //mainClass.MakeTestCase();
                mainClass.Solve();
            }
        }

        public void Dispose()
        {
            if (this.sc != null)
            {
                this.sc.Dispose();
                this.sc = null;
            }
            if (this.wr != null)
            {
                this.wr.Dispose();
                this.wr = null;
            }
        }

        void MakeTestCase()
        {
            Random rand = new Random();
            var res = new StringBuilder();



            using (var writer = new System.IO.StreamWriter(inFilePath))
                writer.Write(res.ToString());
        }

        bool isReactive = true; // TODO: reactive check !!

        void Solve()
        {
            this.wr = new Writer(this.isReactive);
            //wr = new Writer(new System.IO.StreamWriter(this.outFilePath));
#if DEBUG
            if (!this.isReactive)
                this.sc = new Scanner(this.inFilePath);
            else
                this.sc = new Scanner();
#else
            this.sc = new Scanner();
#endif

            Func<int, int> query = (int val) =>
            {
                wr.WriteLine("? " + val);
                return sc.NextInt;
            };
            int cnt = 1;
            int get = query(90);
            if (get <= 0)
            {
                if (get == 0)
                {
                    wr.WriteLine("! " + 90);
                    return;
                }
                for (int i = 1; i <= 90; i++)
                {
                    switch (query(i))
                    {
                        case 1:
                            break;
                        case 0:
                            wr.WriteLine("! " + (i + cnt));
                            return;
                        case -1:
                            wr.WriteLine("! " + (i + cnt - 1));
                            return;
                    }
                    cnt++;
                }
            }
            else
            {
                int low = 0, high = (int)1e9;
                while (high - low > 1)
                {
                    int mid = low + (high - low) / 2;
                    switch (query(mid))
                    {
                        case 1:
                            low = mid;
                            break;
                        case 0:
                            wr.WriteLine("! " + (mid + cnt));
                            return;
                        case -1:
                            high = mid;
                            break;
                    }
                    if (low > 0) low--;
                    high--;
                    cnt++;
                }
                wr.WriteLine("! " + (low + cnt + 1));
            }
        }
    }

    class Writer : IDisposable
    {
        System.IO.TextWriter writer;
        StringBuilder sb;
        bool isReactive;
        public Writer(string path) : this(new System.IO.StreamWriter(path))
        {
        }
        public Writer(bool isReactive) : this(null, isReactive)
        {
        }
        public Writer(System.IO.TextWriter writer = null, bool isReactive = false)
        {
            this.writer = (writer ?? Console.Out);
            if (!(this.isReactive = isReactive))
            {
                this.sb = new StringBuilder();
            }
        }
        public void Dispose()
        {
            if (!isReactive)
                this.writer.Write(sb.ToString());
            if (!this.writer.Equals(Console.Out))
                this.writer.Dispose();
        }
        public void Write(object val)
        {
            if (this.isReactive)
            {
                this.writer.Write(val.ToString());
                this.writer.Flush();
            }
            else
                this.sb.Append(val.ToString());
        }
        public void Write(string format, params object[] vals)
        {
            if (this.isReactive)
            {
                this.writer.Write(format, vals);
                this.writer.Flush();
            }
            else
                this.sb.AppendFormat(format, vals);
        }
        public void WriteLine(object val)
        {
            this.Write(val.ToString() + System.Environment.NewLine);
        }
        public void WriteLine(string format, params object[] vals)
        {
            this.Write(format + System.Environment.NewLine, vals);
        }
    }

    class Scanner : IDisposable
    {
        Queue<string> buffer;
        char[] sep;
        System.IO.TextReader reader;
        public Scanner(string path) : this(new System.IO.StreamReader(path))
        {
        }
        public Scanner(System.IO.TextReader reader = null)
        {
            this.buffer = new Queue<string>();
            this.sep = new char[] { ' ' };
            this.reader = (reader ?? Console.In);
        }
        private void CheckBuffer()
        {
            while (this.buffer.Count == 0)
            {
                string str = this.reader.ReadLine();
                while (string.IsNullOrEmpty(str))
                {
                    str = this.reader.ReadLine();
                }
                string[] sreArray = str.Split(this.sep);
                foreach (string elStr in sreArray)
                {
                    this.buffer.Enqueue(elStr);
                }
            }
        }

        public void Dispose()
        {
            if (!this.reader.Equals(Console.In))
                this.reader.Dispose();
        }

        public string Next
        {
            get
            {
                this.CheckBuffer();
                return this.buffer.Dequeue();
            }
        }

        public int NextInt
        {
            get
            {
                return int.Parse(this.Next);
            }
        }
        public double NextDouble
        {
            get
            {
                return double.Parse(this.Next);
            }
        }

        public long NextLong
        {
            get
            {
                return long.Parse(this.Next);
            }
        }
        public bool IsEmpty
        {
            get
            {
                this.CheckBuffer();
                return this.buffer.Count == 0;
            }
        }
    }
}