#include <iostream>
#include <stdio.h>
#include <cstring>
#include <math.h>
#include <algorithm>
#include <vector>
#define rep(i,n) for(int i=0;i<n;i++)
#define FOR(i,a,b) for(int i=a;i<b;i++)
#define ll long long
#define LL long long
#define mass 1000000007
using namespace std;

int main(){
	int y1=1000000000;
	int sa;
	int y=500000000;
	int res;
	rep(i,100){
		cout<<"? "<<y<<endl;
		cin>>res;
		sa=max(y1-y,y-y1)/2;
		if(sa<=1) break;
		y1=y;
		if(res){
			y=sa+y;
		}else{
			y=y-sa;
		}
	}
	//cout<<"この段階での "<<"res="<<res<<" y="<<y<<endl;
	//int t;
	//cin>>t;
	if(res){
		while(res){
			y++;
			cout<<"? "<<y<<endl;
			cin>>res;
		}
		y--;
	}else{
		while(res==0){
			y--;
			cout<<"? "<<y<<endl;
			cin>>res;
		}
	}
	cout<<"! "<<y<<endl;




	
	return 0;
	

}