import java.util.*;
public class Question{
	public static void main(String... args){
		Scanner scan = new Scanner(System.in);
		System.out.println("! "+String.valueOf(Judge(scan)));
	}
	public static int Judge(Scanner scan){
		int count = 0;
		int high = 1000000000;
		int low = 1;
		int middle = high+low/2;
		int r1 = 0;
		while(count<100){
			System.out.println("? "+middle);
			int res = scan.nextInt();
			if(res == 1){
				low = middle;
				middle = low+high/2;
			}else{
				high = middle;
				middle = low+high/2;
			}

			if(middle+1 == 1 || middle == 0){
				r1=middle+1;
				break;
			}
			if(middle-1 == 1 || middle == 0){
				r1=middle-1;
				break;
			}
			count++;
		}
		return r1;
	}
}