#include <iostream>
#include <cstdio>
using namespace std;

const int INF = 1e+9;

int main() {
	cin.tie(0);
    ios::sync_with_stdio(false);
 
	int lb = 0, ub = INF, res;
	while(ub - lb > 1){
		int mid = (lb + ub) / 2;
		cout << "? " << mid << endl;
		cin >> res;
		if(res){
			lb = mid;
		}
		else{
			ub = mid;
		}
	}
	cout << "! " << ub << endl;
	fflush(stdin);
	return 0;
}