#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int ask(int y) {
	cout << "? " << y << endl;
	int res;
	cin >> res;
	return res;
}

int main()
{
	int cnt = 0;
	int right=0, left = -100;
	int Y = 10;
	while (right<left) {
		Y *= 2;
		if (ask(Y) == -1)right = Y;
		else if (ask(Y) == 0) {
			cout << "! " << Y + cnt << endl;
			return 0;
		}
		cnt++;
	}
	while (left < right) {
		int mid = (left + right) / 2;
		if (ask(mid) == -1)right = mid;
		else if (ask(mid) == 0) {
			cout << "! " << mid + cnt << endl;
			return 0;
		}
		else left = mid+1;
		cnt++;
		right--; left--;
	}

    return 0;
}