import java.util.Scanner;

class Main{
    public static void main(String[] args){
        Scanner sc=new Scanner(System.in);
        int c=1000000000,l=0,n,s=0,t;
        while(true){
            n=(c-l)/2+l;
            if(n==s)++n;
            s=n;
            System.out.println("? "+n);
            System.out.flush();
            t=sc.nextInt();
            if(t>0)l=n;
            else c=n-1;
            if(c==l){
                System.out.println("! "+c);
                System.out.flush();
                break;
            }
        }
        sc.close();
    }
}