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

int cur = 0;

int ask(int l) {
	cout << "? " << l - cur << endl;
	int r; cin >> r; cur++; return r;
}

int main() {
	int ok = 10, ng = 1034;
	while (abs(ok - ng) > 1) {
		int mid = (ok + ng) / 2;
		if (ask(mid) >= 0) ok = mid;
		else ng = mid;
	}
	if (ok < 1000) {
		cout << "! " << ok << endl; return 0;
	}
	ok = 1000, ng = 1e9 + 1;
	while (abs(ok - ng) > 1) {
		int mid = (ok + ng) / 2;
		if (ask(mid) >= 0) ok = mid;
		else ng = mid;
	}
	cout << "! " << ok << endl;
}