#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <math.h>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
using namespace std;

#define ll long long
#define INF (1 << 30)
#define INFLL (1LL << 60)

ll ng = 1000000001,ok = 0,n,mid,re;

int main() {
	while(true){
		mid = (ng + ok) / 2;
		if(ng - 1 != ok){
			cout << "? " << mid << endl;
			cout.flush();
			cin >> re;
			if(re){
				ok = mid;
			}else{
				ng = mid;
			}
		}else{
			cout << "! " << ok << endl;
			cout.flush();
			break;
		}
	}
	return 0;
}