#define _CRT_SECURE_NO_WARNINGS
#include "bits/stdc++.h"
#define rep(i,n) for(int i = 0;i < n;i++)
#define P(p) cout<<(p)<<endl;
using namespace std;
typedef long long ll;
int dx[] = { 0, 1, 0, -1 };
int dy[] = { -1, 0, 1, 0 };

int sttoi(std::string str) {
	int ret;
	std::stringstream ss; ss << str;
	ss >> ret;
	return ret;
}

ll gcd(ll a, ll b){
	if (b > a)swap(a, b); if (b == 0)return a; else{ return gcd(b, a%b); }
}


void solve() {
	int left = 0, right = 1000000000;
	int count = 0;
	cout << "? " << 40 << endl;
	int s;
	cin >> s;
	if (s == -1){
		for (int i = 1;;i++){
			cout << "? " << 0 << endl;
			cin >> s;
			if (s == 0){
				cout << "! " << i << endl;
				return;
			}
		}
	}
	for (int i = 1; i <= 100;i++){
		int mid = left + right;
		mid /= 2;
		cout << "? " << mid-i << endl;
		int a;
		cin >> a;
		count++;
		if (a == 0){
			cout << "! " << mid << endl; return;
		}
		else if (a == 1){
			left = mid + 1;
		}
		else if (a == -1){
			right = mid;
		}
	}
}

int main() {
	solve();
	return 0;
}