package q5xx;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Scanner;

public class Q551 {
	static Scanner in;
	static PrintWriter out;
	static String INPUT = "";
	
	static void solve()
	{
		int low = 1, high = 1000000000+1;
		while(high - low > 1){
			int h = high+low>>>1;
			if(go(h)){
				low = h;
			}else{
				high = h;
			}
		}
		out.println("! " + low);
	}
	
	static boolean go(int h)
	{
		out.println("? " + h);
		out.flush();
		
		return ni() == 1;
	}
	
	public static void main(String[] args) throws Exception
	{
		in = INPUT.isEmpty() ? new Scanner(System.in) : new Scanner(INPUT);
		out = new PrintWriter(System.out);
		
		solve();
		out.flush();
	}
	
	static int ni() { return Integer.parseInt(in.next()); }
	static long nl() { return Long.parseLong(in.next()); }
	static double nd() { return Double.parseDouble(in.next()); }
	static void tr(Object... o) { if(INPUT.length() != 0)System.out.println(Arrays.deepToString(o)); }
}