import java.util.*;
import java.math.*;
import java.text.*;

public class Main {
    private static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) throws Exception {
        int ans = 500000000;
        int s = 1;
        int e = 1000000000;
        while (true) {
            System.out.println("? " + ans);
            System.out.flush();
            int ret = sc.nextInt();
            if (ret == 1) {
                s = ans;
            } else {
                e = ans-1;
            }
            ans = (s+e)/2+1;
            
            if (s == e) {
                System.out.println("! " + s);
            }
        }
    }
}