import java.util.*;
public class Main{
    public static void main(String[] V){
        Scanner sc = new Scanner(System.in);
        int L = 1;
        int R = 1000000001;
        while(R - L > 1){
            int C = (L + R) / 2;
            System.out.println("? " + C);
            System.out.flush();
            int isOK = sc.nextInt();
            if(isOK == 1){
                L = C;
            }else{
                R = C;
            }
        }
        System.out.println("! " + R);
        System.out.flush();
    }
}