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

public class Q687 {
	static Scanner in;
	static PrintWriter out;
	static String INPUT = "";
	
	static void solve()
	{
		long low = 10, high = 1000000001;
		int turn = 0;
		for(long i = low;;i*=2){
			out.println("? " + i);
			out.flush();
			int res = ni();
			if(res == 0){
				low = i+turn; high = i+turn;
				out.println("! " + low);
				out.flush();
				return;
			}else if(res == 1){
				low = i+1+turn;
			}else{
				high = i+turn;
				break;
			}
			turn++;
		}
		turn++;
		while(true){
			long h = (high-turn)+(low-turn)>>>1;
			out.println("? " + h);
			out.flush();
			int res = ni();
			if(res == 0){
				low = h+turn; high = h+turn;
				out.println("! " + low);
				out.flush();
				return;
			}else if(res == 1){
				low = h+1+turn;
			}else{
				high = h+turn;
			}
			turn++;
		}
	}
	
	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)); }
}