#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <climits>
#include <cmath>
#include <string>
#include <vector>
#include <algorithm>
#include <queue>
#include <map>
#include <functional>
#include <set>
#include <numeric>
#include <stack>
#include <utility>
#include <time.h>
//#include "util.h"

using namespace std;
typedef unsigned uint;
typedef long long ll;
typedef unsigned long long ull;



//呪文
template <typename _KTy, typename _Ty> ostream& operator << (ostream& ostr, const pair<_KTy, _Ty>& m) { cout << "{" << m.first << ", " << m.second << "}"; return ostr; }
template <typename _KTy, typename _Ty> ostream& operator << (ostream& ostr, const map<_KTy, _Ty>& m) { if (m.empty()) { cout << "{ }"; return ostr;	} cout << "{" << *m.begin(); for (auto itr = ++m.begin(); itr != m.end(); itr++) { cout << ", " << *itr; } cout << "}"; return ostr; }
template <typename _Ty> ostream& operator << (ostream& ostr, const vector<_Ty>& v) { if (v.empty()) { cout << "{ }"; return ostr; }	cout << "{" << v.front(); for (auto itr = ++v.begin(); itr != v.end(); itr++) { cout << ", " << *itr; }	cout << "}"; return ostr; }
template <typename _Ty> ostream& operator << (ostream& ostr, const set<_Ty>& s) { if (s.empty()) { cout << "{ }"; return ostr; } cout << "{" << *(s.begin()); for (auto itr = ++s.begin(); itr != s.end(); itr++) { cout << ", " << *itr; }	cout << "}"; return ostr; }
#define PI 3.14159265358979323846
#define EPS 1e-6
#define MIN(a,b) ((a)<(b)?(a):(b))
#define MAX(a,b) ((a)>(b)?(a):(b))
#define all(x) (x).begin(), (x).end()



int yuki0246()
{
	int l, m, r;
	bool f;

	l = 0; r = 1000000000;
	while (r - l > 1) {
		m = (l + r) / 2;
		cout << "? " << m << endl;

		cin >> f;

		if (f) l = m;
		else r = m - 1;
	}

	for (int i = l - 1; i <= r + 1; i++) {
		cout << "? " << i << endl;
		cin >> f;
		if (!f) {
			cout << "! " << i - 1 << endl;
			return 0;
		}
	}

	return 0;
}

int main()
{
	//clock_t start, end;
	//start = clock();

	yuki0246();
	
	//end = clock();
	//printf("%d msec.\n", end - start);

	return 0;
}