#include <iostream>
using namespace std;

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

int solve(){
	int askCount = 0;
	for(int i=2;i<=50;i++,askCount++){
		int res = ask(i);
		if(res < 0){
			return i - 1 + askCount;
		}
		if(res == 0){
			return i + askCount;
		}
	}
	// [lo, hi]
	int lo = 50, hi = 1e9 - askCount;
	for(;;++askCount){
		int mid = (lo + hi) / 2;
		int res = ask(mid);
		if(res == 0){
			return mid + askCount;
		}
		if(res < 0){
			hi = mid - 1;
		} else {
			lo = mid + 1;
		}
		if(lo == hi){
			return lo + askCount;
		}
		--lo;
		--hi;
	}
	return -1;
}

int main(){
	int Y = solve();
	cout << "! " << Y << endl;
	return 0;
}