package yukicoder246;
import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		int upper=(int)Math.pow(10, 9);
		int low=0;
		
		while(upper!=low){
			int mid=(int)(upper+low)/2;
			System.out.println("?"+mid);
			int a=sc.nextInt();
			if(a==1){
				low=mid;
				if(upper==low+1){
					System.out.println("!"+upper);
					sc.close();
					return;
				}
			}else{
				upper=mid;
				if(upper==low){
					System.out.println("!"+upper);
					sc.close();
					return;
				}
			}
		}
		
	}
}