import java.util.Scanner;

public class Yukicoder246 {

    public static void main(String[] args) {
        int min = 0, max = 1000000000, mid;
        Scanner sc = new Scanner(System.in);
        while (Math.abs(max-min) > 1) {
            mid = (max + min) / 2;
            System.out.println("? " + mid);
            if (sc.nextInt() == 1) min = mid;
            else max = mid;
        }
        System.out.println("! " + min);
    }
}