#include <iostream>
#include <vector>
#include <cstdio>
#include <sstream>
#include <map>
#include <string>
#include <algorithm>
#include <queue>
#include <cmath>
#include <set>
using namespace std;

int main(){
	long long lb = 1;
	long long ub = 1e9 + 1;
	while(ub - lb > 1){
		long long mid = (lb+ub)/2;
		cout << "? " << mid << endl;
		int res;
		cin >> res;
		if(res == 1){
			lb = mid;
		}else{
			ub = mid;
		}
	}
	cout << "! " << lb << endl;
	return 0;
}