using System;

public class Program
{
	public static void Main()
	{
		int min = 1, max = (int)Math.Pow(10, 9);
		int mid = (int)Math.Ceiling((min + max) / 2.0);
		for (; min != max; mid = (int)Math.Ceiling((min + max) / 2.0))
		{
			Console.WriteLine("? {0}", mid);
			bool isLess = int.Parse(Console.ReadLine()) == 0;
			if (isLess)
			{
				max = mid - 1;
			}
			else
			{
				min = mid;
			}
		}
		Console.WriteLine("! {0}", mid);
	}
}