import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int l = 1;
		int r = 1000000000;
		int mid = (l + r) / 2;
		int cnt = 0;
		int n = mid;
		for(int i = 0; i < 100; i++) {
			System.out.println("? " + mid);
			int t = scan.nextInt();
			if(t == 1) {
				l = mid;
				mid = (l + r) / 2;
			}else {
				r = mid;
				mid = (l + r) / 2;
			}
			if(n == mid) {
				cnt++;
			}else {
				cnt = 0;
				n = mid;
			}
			if(r - l == 1) {
				System.out.println("! " + mid);
				System.exit(0);
			}

		}
		scan.close();
	}
}