#include <bits/stdc++.h>
using namespace std;

#define rep(i,x,y) for(int i=(x);i<(y);++i)
#define mp(a,b) make_pair((a),(b))
#define debug(x) #x << "=" << (x)
 
#ifdef DEBUG
#define _GLIBCXX_DEBUG
#define dump(x) std::cerr << debug(x) << " (L:" << __LINE__ << ")" << std::endl
#else
#define dump(x)
#endif

typedef long long int ll;
typedef pair<int,int> pii;
//template<typename T> using vec=std::vector<T>;

const int INF=1<<30;
const long long int LLNF_=1LL<<58;
const double EPS=1e-9;
const int dx[]={1,0,-1,0},dy[]={0,1,0,-1};

template <typename T> ostream &operator<<(ostream &os, const vector<T> &vec){
	os << "[";
	for (const auto &v : vec) {
		os << v << ",";
	}
	os << "]";
	return os;
}

void Solve(){
	{
		int res;
		cout << "? " << 50 << endl;
		cin >> res;
		if(res==-1){
			int k=1;
			while(true){
				cout << "? " << 0 << endl;
				cin >> res;
				if(res==0){
					cout << "! " << k << endl;
					return;
				}
				++k;
			}
		}
	}
	
	int lb=10,ub=1000000001,k=1;
	while(true){
		int mid=(lb+ub)/2,res;
		cout << "? " << mid << endl;
		cin >> res;
		if(res==0){
			cout << "! " << mid+k << endl;
			break;
		}else if(res==-1) ub=mid;
		else lb=mid;
		--lb;
		--ub;
		if(lb<0) lb=0;
		if(ub<0) ub=0;
		++k;
	}
}

int main(){
	Solve();
	return 0;
}