import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int min=1;
        int max=1000000000;
        while(true){
            int mid=max-(max-min)/2;
            System.out.println("? "+mid);
            System.out.flush();
            int x = sc.nextInt();
            if(x==1){
                min=mid;
            }else{
                max=mid-1;
            }
            if(max==min){
                System.out.println("! "+max);
                break;
            }
        }
    }
}