import java.util.Scanner;

public class Yuki_Reactive {

    public Yuki_Reactive() {
        Scanner scanner = new Scanner(System.in);
        int[] dummy = new int[100000000];
        int A = 0;
        int B = (int) (1e+9) + 1;
        while (B - A > 1) {
            int c = (B + A) / 2;
            System.out.println("? " + c);
//            System.out.flush();
            final int response = scanner.nextInt();
            if (response == 1) {
                A = c;
            } else {
                B = c;
            }
        }
        System.out.println("! " + A );
        System.out.flush();

    }

    public static void main(String[] args) {
        Yuki_Reactive hoge = new Yuki_Reactive();
    }
}