import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int[] x = new int[25];
		System.out.println("? 0");
		int i = 0;
		int ok = 1000000;
		int ng = 0;
		while (Math.abs(ok - ng) > 1) {
			int mid = (ok + ng) / 2;
			int cx = x[i];
			i++;
			int nx = mid * 2 - cx;
			x[i] = nx;
			System.out.println("? " + nx);
			int res = sc.nextInt();
			if (cx < nx) {
				if (res == 0) {
					ok = mid;
				} else {
					ng = mid;
				}
			} else {
				if (res == 1) {
					ok = mid;
				} else {
					ng = mid;
				}
			}
		}
		System.out.println("! " + ok);
		sc.close();
	}
}