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

int ask(int y){
	cout<<"? "<<y<<endl;
	int res;
	return res;
}

int solve(int l,int r){
	if(l-r==1)return l;
	if(l==0){
		int a=ask(1);
		if(a==-1)return 0;
		else if(a==0)return 1;
		else return 1+solve(1,r-1);
	}else{
		int mid=l+(r-l)/2;
		int a=ask(mid);
		if(a==0)return mid;
		else if(a==-1)return 1+solve(l-1,mid-1);
		else return 1+solve(mid,r-1);
	}
}

int main(){
	cout<<"! "<<solve(0,1e9+1)<<endl;
}