#include <bits/stdc++.h>
using namespace std;

int ask(int x)
{
	static int cnt = 0;
	int res;
	cout << "? " << max(0, x - cnt++) << endl;
	cin >> res;
	return res;
}

int solve()
{
	if (ask(40) == -1){
		for (int i = 1;; i++){
			if (ask(i) == 0) return i;
		}
	}
	
	int l = 0, r = 1e9 + 10;
	while (l + 1 < r){
		int m = (l + r) / 2;
		if (ask(m) == 0) return m;
		if (ask(m) == -1) r = m;
		else l = m;
	}
}

int main()
{
	cout << "! " << solve() << endl;
}