using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.IO;
using System.Threading.Tasks;
using static System.Console;
using static System.Math;

using P=System.Tuple<long,long>;

namespace Tasks{

    public class Program{
     
        public static void Main(string[] args){
            var sw = new StreamWriter(Console.OpenStandardOutput()){AutoFlush = false};
            Console.SetOut(sw);
            new Program().Solve(new ConsoleInput(Console.In, ' '));
            Console.Out.Flush();
        }
        
        public void Solve(ConsoleInput cin){
            long ok=0,ng=pow(10,9)+1;
            long mid=(ok+ng)/2;
            while(ng-ok>1){
                Out("? "+mid);
                Console.Out.Flush();
                int res=cin.nextint;
                if(res==1) ok=mid;
                else if(res==0) ng=mid;
                mid=(ok+ng)/2;
            }
            Out("! "+ok);
        }
       
       
        public List<List<int>> graph(int n,int m,bool edge=false){
            List<List<int>> g=new List<List<int>>();
            for(int i=0;i<n;++i) g.Add(new List<int>());
            for(int i=0;i<m;++i){
                var cin =new ConsoleInput(Console.In, ' ');
                int u=cin.nextint-1,v=cin.nextint-1;
                g[u].Add(v);
                if(!edge) g[v].Add(u);
            }
            return g;
        }
        
        public static bool inrange(int y, int x, int h, int w) { return 0 <= x && x < w && 0 <= y && y < h; }
        
        public static void Out<T>(params T[] A){
            int n=A.Length;
            for(int i=0;i<n;++i){
                if(i!=n-1){
                    if(typeof(T)==typeof(double)){
                        Write("{0:f12}",A[i]);
                        Write(" ");
                    }
                    else Write(A[i]+" ");
                }
                else{
                    if(typeof(T)==typeof(double)){
                        WriteLine("{0:f12}",A[i]);
                    }
                    else WriteLine(A[i]);
                }
            }
        }
        public static void Out(){WriteLine();}
        
    
        public static void Yes(bool ok) => Console.WriteLine(ok ? "Yes": "No");
        public static void YES(bool ok) => Console.WriteLine(ok ? "YES": "NO");
        
        static void chmax(ref long m, long v, long mod = -1) { m = Math.Max(m, v); if (mod != -1) m %= mod; }
        static void chmax(ref int m, int v) { m = Math.Max(m, v);}
        static void chmin(ref long m, long v, long mod = -1) { m = Math.Min(m, v); if (mod != -1) m %= mod; }
        static void chmin(ref int m, int v) { m = Math.Min(m, v);}
        static void swap<T>(ref T a, ref T b) { var w = a; a = b; b = w; }
        
        static void Fill<T>(T[] array, T x) { for (int i = 0; i < array.Length; i++) { array[i] = x; } }
        static void Fill<T>(T[,] array, T x) { for (int i = 0; i < array.GetLength(0); i++){
            for (int j = 0; j < array.GetLength(1); j++) array[i, j] = x; }    
        }
        
        static void Showarray<T>(T[,] array){
            for(int i=0;i<array.GetLength(0);i++){
                for(int j=0;j<array.GetLength(1);j++){
                    Write(array[i,j]+" ");
                }
                WriteLine();
            } 
        }
        static T[,] Rotatearray<T>(T[,] array) {
            int h=array.GetLength(0);
            int w=array.GetLength(1);
            var array2 = new T[w,h];
            for (int i = 0; i < h; i++)for (int j = 0; j < w; j++){
                array2[j,h - i - 1] = array[i, j];
            }
            return array2;
        }
        
        public static void OutAllLine<T>(IEnumerable<T> items)
            {
                var sb = new StringBuilder();
                foreach (T result in items)
                {
                    sb.Append(result + "\n");
                }
     
                sb = sb.Remove(sb.Length - 1, 1);
                Console.WriteLine(sb);
            }
        
        public static void OutEachSpace<T>(IEnumerable<T> items)
            {
                var sb = new StringBuilder();
                foreach (T result in items)
                {
                    sb.Append(result + " ");
                }
     
                sb = sb.Remove(sb.Length - 1, 1);
                Console.WriteLine(sb);
            }
        
        static List<T[]> AllPermutation<T>(params T[] array) where T : IComparable
        {
            var a = new List<T>(array).ToArray();
            var res = new List<T[]>();
            res.Add(new List<T>(a).ToArray());
            var n = a.Length;
            var next = true;
            while (next)
            {
                next = false;
     
                int i;
                for (i = n - 2; i >= 0; i--)
                {
                    if (a[i].CompareTo(a[i + 1]) < 0) break;
                }
                
                if (i < 0) break;
     
           
                var j = n;
                do
                {
                    j--;
                } while (a[i].CompareTo(a[j]) > 0);
     
                if (a[i].CompareTo(a[j]) < 0)
                {
               
                    var tmp = a[i];
                    a[i] = a[j];
                    a[j] = tmp;
                    Array.Reverse(a, i + 1, n - i - 1);
                    res.Add(new List<T>(a).ToArray());
                    next = true;
                }
            }
            return res;
        }
        
        public static T max<T>(params T[] A)  where T : IComparable
        {
            int n=A.Length;
            T max=A[0];
            for(int i=1;i<n;++i){
                max=max.CompareTo(A[i]) > 0 ? max:A[i];
            }
            return max;
        }
        public static T min<T>(params T[] A)  where T : IComparable
        {
            int n=A.Length;
            T min=A[0];
            for(int i=1;i<n;++i){
                min=min.CompareTo(A[i]) < 0 ? min:A[i];
            }
            return min;
        }
        
        static long pow(long a,long n){
            long ret=1;
            while(n>0){
                if((n&1)>0) ret*=a;
                a=a*a;
                n>>=1;
            }
            return ret;
        }
        static long modpow(long a,long n, long mod){
            long ret=1;
            while(n>0){
                if((n&1)>0) ret=ret*a%mod;
                a=a*a%mod;
                n>>=1;
            }
            return ret;
        }
        
        public static long modinv( long a, long mod ){
            return modpow(a,mod-2,mod);
        }
    
        static long Lcm(long a, long b){return a / Gcd(a, b) * b;}
        
        static long Gcd(long m, long n){if (n == 0) return m;return Gcd(n, m % n);}
        
        public static int LowerBound<T>(T[] arr, int start, int end, T value, IComparer<T> comparer)
        {
            int low = start;
            int high = end;
            int mid;
            while (low < high)
            {
                mid = ((high - low) >> 1) + low;
                if (comparer.Compare(arr[mid], value) < 0)
                    low = mid + 1;
                else
                    high = mid;
            }
            return low;
        }

        public static int LowerBound<T>(T[] arr, T value) where T : IComparable
        {
            return LowerBound(arr, 0, arr.Length, value, Comparer<T>.Default);
        }
        
        public static int UpperBound<T>(T[] arr, int start, int end, T value, IComparer<T> comparer)
        {
            int low = start;
            int high = end;
            int mid;
            while (low < high)
            {
                mid = ((high - low) >> 1) + low;
                if (comparer.Compare(arr[mid], value) <= 0)
                    low = mid + 1;
                else
                    high = mid;
            }
            return low;
        }
    
        public static int UpperBound<T>(T[] arr, T value)
        {
            return UpperBound(arr, 0, arr.Length, value, Comparer<T>.Default);
        }
    
    
        public static Dictionary<long, long> PrimeFactorization(long n)
        {
            var result = new Dictionary<long, long>();
     
            for (long i = 2; i * i <= n; i++)
            {
                if (n % i != 0) continue;
                long exponents = 0;
     
            
                while (n % i == 0)
                {
                    exponents++;
                    n /= i;
                }
     
                result[i] = exponents;
            }
     
       
            if (n != 1) result[n] = 1;
            return result;
        }
        
        public static bool Isprime(long num)
            {
                if (num < 2) { return false; }
     
                if (num == 2) { return true; }
     
                if (num % 2 == 0) { return false; }
     
                double sqrtNum = Math.Sqrt(num);
                for (int i = 3; i <= sqrtNum; i += 2)
                {
                    if (num % i == 0) { return false; }
                }
     
                return true;
            }
        
        public static long[] GetDivisors(long n)
            {
                HashSet<long> divisors = new HashSet<long>();
     
                for (long i = 1; i * i <= n; i++)
                {
                    if (n % i != 0) { continue; }
     
                    divisors.Add(i);
                    divisors.Add(n / i);
                }
     
                return divisors.OrderBy(x => x).ToArray();
            }
        
        public static bool[] PrimeTable(int n) 
            {
                var prime = new bool[n + 1];
                for(int i=0;i<=n;i++) prime[i]=true;
                if (n >= 0) prime[0] = false;
                if (n >= 1) prime[1] = false;
                for (int i = 2; i * i <= n; i++){
                    if (!prime[i]) continue;
                    for (int j = i * i; j <= n; j += i) prime[j] = false;
                }
                return prime;
            }
            
        static int lis(int[] a){
            const int inf=(1<<30);
            int n=a.Length;
            int[] dp=new int[n+1];
            Fill(dp,inf);
            for(int i=0;i<n;++i){
                int idx=LowerBound(dp,a[i]);
                dp[idx]=a[i];
            }
            int ret=LowerBound(dp,inf);
            return ret;
        }
        
        static int[,] lcs(char[] s,char[] t){
            int n=s.Length,m=t.Length;
            int[,] dp=new int[n+1,m+1];
            for(int i=0;i<n;++i){
                for(int j=0;j<m;++j){
                    if(s[i]==t[j]) dp[i+1,j+1]=dp[i,j]+1;
                    else dp[i+1,j+1]=max(dp[i+1,j],dp[i,j+1]);
                }
            }
            return dp;
        }
        
        static long inversionnum(int[] array){
            int n=array.Length;
            if(n==0) return 0;
            int[] copy=new int[n];
            Array.Copy(array,copy,n);
            Array.Sort(copy);
            int[] bit=new int[n+1];
            long ans=((long)n*(n-1)) >> 1;
            for(int i=0;i<n;++i){
                int min=0,max=n;
                int comp=array[i];
                while(max-min>1){
                    int mid=(min+max) >> 1;
                    if(copy[mid]<=comp) min=mid;
                    else max=mid;
                }
                for(int j=max; j>0;j-=j&-j) ans-=bit[j];
                for(int j=max;j<n+1;j+=j&-j) ++bit[j];
            }
            return ans;
        }
        
    }
    
    class Dikstra
    {
        public int N { get; }            
        private List<Edge>[] _graph;  
        
        public Dikstra(int n)
        {
            N = n;
            _graph = new List<Edge>[n];
            for (int i = 0; i < n; i++) _graph[i] = new List<Edge>();
        }
    
        public void Add(int a, int b, long cost = 1)
                => _graph[a].Add(new Edge(b, cost));
    
        public long[] GetMinCost(int start)
        {
            var cost = new long[N];
            for (int i = 0; i < N; i++) cost[i] = ((long)1<<60);
            cost[start] = 0;
    
    
            var q = new PriorityQueue<Vertex>(isDescending:false);
            q.Enqueue(new Vertex(start, 0));
    
            while (q.Count > 0)
            {
                var v = q.Dequeue();
    
               
                if (v.cost != cost[v.index]) continue;
    
               
                foreach (var e in _graph[v.index])
                {
                    if (cost[e.to] > v.cost + e.cost)
                    {
                        
                        cost[e.to] = v.cost + e.cost;
                        q.Enqueue(new Vertex(e.to, cost[e.to]));
                    }
                }
            }
    
            
            return cost;
        }
    
        public struct Edge
        {
            public int to;                      
            public long cost;                  
    
            public Edge(int to, long cost)
            {
                this.to = to;
                this.cost = cost;
            }
        }
    
        public struct Vertex : IComparable<Vertex>
        {
            public int index;                  
            public long cost;                  
    
            public Vertex(int index, long cost)
            {
                this.index = index;
                this.cost = cost;
            }
    
            public int CompareTo(Vertex other)
                => cost.CompareTo(other.cost);
        }
    }
   
    class PriorityQueue<T> : IEnumerable<T>
    {
        private readonly List<T> _data = new List<T>();
        private readonly IComparer<T> _comparer;
        private readonly bool _isDescending;
    
        public PriorityQueue(IComparer<T> comparer, bool isDescending = true)
        {
            _comparer = comparer;
            _isDescending = isDescending;
        }
    
        public PriorityQueue(Comparison<T> comparison, bool isDescending = true)
            : this(Comparer<T>.Create(comparison), isDescending)
        {
        }
    
        public PriorityQueue(bool isDescending = true)
            : this(Comparer<T>.Default, isDescending)
        {
        }
    
        public void Enqueue(T item)
        {
            _data.Add(item);
            var childIndex = _data.Count - 1;
            while (childIndex > 0)
            {
                var parentIndex = (childIndex - 1) / 2;
                if (Compare(_data[childIndex], _data[parentIndex]) >= 0)
                    break;
                Swap(childIndex, parentIndex);
                childIndex = parentIndex;
            }
        }
    
        public T Dequeue()
        {
            var lastIndex = _data.Count - 1;
            var firstItem = _data[0];
            _data[0] = _data[lastIndex];
            _data.RemoveAt(lastIndex--);
            var parentIndex = 0;
            while (true)
            {
                var childIndex = parentIndex * 2 + 1;
                if (childIndex > lastIndex)
                    break;
                var rightChild = childIndex + 1;
                if (rightChild <= lastIndex && Compare(_data[rightChild], _data[childIndex]) < 0)
                    childIndex = rightChild;
                if (Compare(_data[parentIndex], _data[childIndex]) <= 0)
                    break;
                Swap(parentIndex, childIndex);
                parentIndex = childIndex;
            }
            return firstItem;
        }
    
        public T Peek()
        {
            return _data[0];
        }
    
        private void Swap(int a, int b)
        {
            var tmp = _data[a];
            _data[a] = _data[b];
            _data[b] = tmp;
        }
    
        private int Compare(T a, T b)
        {
            return _isDescending ? _comparer.Compare(b, a) : _comparer.Compare(a, b);
        }
    
        public int Count => _data.Count;
    
        public IEnumerator<T> GetEnumerator()
        {
            return _data.GetEnumerator();
        }
    
        IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
    }
            
    class UnionFind{
        private int[] _unionfind;
        private int[] _unionfind_size;
        
        public UnionFind(int a){
            _unionfind = new int[a];
            _unionfind_size = new int[a];
            for(int i=0;i<a;i++){
                _unionfind[i] = i;
                _unionfind_size[i] = 1;
            }
        }
        
        public int Root(int x){
            if(_unionfind[x] == x) return x;
            return _unionfind[x] = Root(_unionfind[x]);
        }
        
        public void Unite(int a,int b){
            a = Root(a);
            b = Root(b);
            if(a == b) return;
            if(_unionfind_size[a] < _unionfind_size[b]){
                int temp = a;
                a = b;
                b = temp;
            }
            _unionfind[b] = a;
            _unionfind_size[a] += _unionfind_size[b];
        }
        
        public bool Same(int a,int b){
            return Root(a) == Root(b);
        }
        
        public int Size(int x){
            return _unionfind_size[Root(x)];
        }
    }
    
    
    public class SegmentTree<T>
    {
        public int N { get; private set; }
        private T[] _tree;
        private readonly Func<T, T, T> _updateMethod;
        private readonly T _initValue;
    
        
        public SegmentTree(IEnumerable<T> items, Func<T, T, T> updateMethod, T initValue) {
            T[] array = items.ToArray();
            _updateMethod = updateMethod;
            _initValue = initValue;
    
           
            N = 1;
            while (N < array.Length) N *= 2;
    
            _tree = Enumerable.Repeat(initValue, 2 * N - 1).ToArray();
    
            for (int i = 0; i < array.Length; i++) _tree[N + i - 1] = array[i];
            for (int i = N - 2; i >= 0; i--) _tree[i] = _updateMethod(_tree[2 * i + 1], _tree[2 * i + 2]);
        }
 
        public void Update(int i, T x)
        {
        
            i = N + i - 1;
    
            _tree[i] = x;
            while(i > 0)
            {
                i = (i - 1) / 2;
                _tree[i] = _updateMethod(_tree[2 * i + 1], _tree[2 * i + 2]);
            }
        }
    
 
        public T Execute(int a, int b)
            => Execute(a, b, 0, 0, N);
    
        private T Execute(int a, int b, int k, int l, int r)
        {
    
            if (r <= a || b <= l) return _initValue;
    
            if (a <= l && r <= b) return _tree[k];
    
            var vl = Execute(a, b, 2 * k + 1, l, (l + r) / 2);
            var vr = Execute(a, b, 2 * k + 2, (l + r) / 2, r);
            return _updateMethod(vl, vr);
        }
    }
    
    class Deque<T> : IEnumerable<T>
    {
        public T this[int i]
        {
            get { return this.Buffer[(this.FirstIndex + i) % this.Capacity]; }
            set
            {
                if (i < 0) throw new ArgumentOutOfRangeException();
                this.Buffer[(this.FirstIndex + i) % this.Capacity] = value;
            }
        }
        private T[] Buffer;
        private int Capacity;
        private int FirstIndex;
        private int LastIndex
        {
            get { return (this.FirstIndex + this.Length) % this.Capacity; }
        }
        public int Length;
        public Deque(int capacity = 16)
        {
            this.Capacity = capacity;
            this.Buffer = new T[this.Capacity];
            this.FirstIndex = 0;
        }
        public void PushBack(T data)
        {
            if (this.Length == this.Capacity) this.Resize();
            this.Buffer[this.LastIndex] = data;
            this.Length++;
        }
        public void PushFront(T data)
        {
            if (this.Length == this.Capacity) this.Resize();
            var index = this.FirstIndex - 1;
            if (index < 0) index = this.Capacity - 1;
            this.Buffer[index] = data;
            this.Length++;
            this.FirstIndex = index;
        }
        public T PopBack()
        {
            if (this.Length == 0) throw new InvalidOperationException("There is no data available.");
            var data = this[this.Length - 1];
            this.Length--;
            return data;
        }
        public T PopFront()
        {
            if (this.Length == 0) throw new InvalidOperationException("There is no data available.");
            var data = this[0];
            this.FirstIndex++;
            this.FirstIndex %= this.Capacity;
            this.Length--;
            return data;
        }
        private void Resize()
        {
            var newArray = new T[this.Capacity * 2];
            for (int i = 0; i < this.Length; i++)
            {
                newArray[i] = this[i];
            }
            this.FirstIndex = 0;
            this.Capacity *= 2;
            this.Buffer = newArray;
        }
        public IEnumerator<T> GetEnumerator()
        {
            for (int i = 0; i < this.Length; i++)
            {
                yield return this[i];
            }
        }
        IEnumerator IEnumerable.GetEnumerator()
        {
            for (int i = 0; i < this.Length; i++)
            {
                yield return this[i];
            }
        }
    }
            
    public class ConsoleInput
    {
        private readonly System.IO.TextReader _stream;
        private char _separator = ' ';
        private Queue<string> inputStream;
        public ConsoleInput(System.IO.TextReader stream, char separator = ' ')
        {
            this._separator = separator;
            this._stream = stream;
            inputStream = new Queue<string>();
        }
        public string Read
        {
            get
            {
                if (inputStream.Count != 0) return inputStream.Dequeue();
                string[] tmp = _stream.ReadLine().Split(_separator);
                for (int i = 0; i < tmp.Length; ++i)
                    inputStream.Enqueue(tmp[i]);
                return inputStream.Dequeue();
            }
        }
        public string next { get { return _stream.ReadLine(); }}
        public int nextint { get { return int.Parse(Read); }}
        public long nextlong { get { return long.Parse(Read); }}
        public double nextdouble { get { return double.Parse(Read); }}
        
        public string[] strarray(long N) { var ret = new string[N]; for (long i = 0; i < N; ++i) ret[i] = Read; return ret;}
        public int[] intarray(long N) { var ret = new int[N]; for (long i = 0; i < N; ++i) ret[i] = nextint; return ret;}
        public long[] longarray(long N) { var ret = new long[N]; for (long i = 0; i < N; ++i) ret[i] = nextlong; return ret;}
        public int[,] intarray2(long h,long w){
            var ret=new int[h,w];
            for(long i=0;i<h;++i) {
                int[] tmparray=intarray(w);
                for(long j=0;j<w;++j) ret[i,j]=tmparray[j];
            } 
            return ret;
        }
        public long[,] longarray2(long h,long w){
            var ret=new long[h,w];
            for(long i=0;i<h;++i) {
                long[] tmparray=longarray(w);
                for(long j=0;j<w;++j) ret[i,j]=tmparray[j];
            } 
            return ret;
        }
        public char[] chararray(long N){var ret=new char[N]; string tmp=next;for(int i=0;i<N;++i) ret[i]=tmp[i]; return ret;}
        public char[,] chararray2(long h,long w){
            var ret=new char[h,w];
            for(int i=0;i<h;++i){
                char[] tmparray=chararray(w);
                for(int j=0;j<w;++j) ret[i,j]=tmparray[j];
            }
            return ret;
        }
        public void array2(long[] A,long[] B){
            int n=A.Length; for(int i=0;i<n;++i){A[i]=nextlong;B[i]=nextlong;}
        }
        public void array2(int[] A, int[] B){
            int n=A.Length; for(int i=0;i<n;++i){A[i]=nextint;B[i]=nextint;}
        }
        public void array3(long[] A,long[] B,long[] C){
            int n=A.Length; for(int i=0;i<n;++i){A[i]=nextlong;B[i]=nextlong;C[i]=nextlong;}
        }
        public void array3(int[] A,int[] B,int[] C){
            int n=A.Length; for(int i=0;i<n;++i){A[i]=nextint;B[i]=nextint;C[i]=nextint;}
        }

    }
}