using System;

public class Program
{
	public static void Main()
	{
		int max = (int)1e9, min = 1;
		while (max != min)
		{
			int mid = (max + min) / 2;
			Console.WriteLine($"? {mid}");
			int result = int.Parse(Console.ReadLine());
			if (result == 1)
			{
				min = mid;
			}
			else
			{
				max = mid - 1;
			}
		}
		Console.WriteLine($"! {max}");
	}
}