import java.util.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		int left = 0;
		int right = Integer.MAX_VALUE / 2;
		while (right - left > 1) {
		    int m = (left + right) / 2;
		    System.out.println("? " + m) ;
		    System.out.flush();
		    int judge = sc.nextInt();
		    if (judge == 0) {
		        left = m;
		    } else {
		        right = m;
		    }
		}
		System.out.println("! " + right);
		System.out.flush();
	}
}