#include <iostream>
#include <string>
#include <iomanip>
using namespace std;

int main(){
	int max = 1000000000, min = 1, mid = (min + max) / 2;
	int res;
	
	while(min - max > 1){
		cout << "? " << mid << endl << flush;
		cin >> res;
		if(res){
			min = mid;
		}else{
			max = mid;
		}
		
		mid = (min + max) / 2;
	}
	cout << "! " << mid << endl;
	
	return 0;
}