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

int main(){
	long long data;
	long long right = 1000000000, left = 1, mid;
	int count = 0;
	while(1){
		mid = (right+left) / 2;
		cout << "? " << mid << endl;
		cin >> data;
		if(count == mid){
			cout << "! " << mid << endl;
			break;
		}
		if(data){
			left = mid + 1;
			count = mid;
		}else{
			right = mid - 1;
			count = mid;
		}
	}
	return 0;
}