import java.util.*;

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