using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var prev = 1;
        var cur = 1_000_000;
        WriteLine($"? {prev}");
        var left = prev;
        var right = cur;
        while (right > left)
        {
            WriteLine($"? {cur}");
            var ans = NN;
            if (ans == -1) return;
            if (ans == 1)
            {
                if (prev < cur)
                {
                    left = (prev + cur + 1) / 2;
                }
                else
                {
                    right = (prev + cur) / 2;
                }
            }
            else
            {
                if (prev < cur)
                {
                    right = (prev + cur - 1) / 2;
                }
                else
                {
                    left = (prev + cur) / 2 + 1;
                }
            }
            prev = cur;
            var mid2 = left + right;
            var cur2 = cur * 2;
            cur = (cur2 + (mid2 - cur2) * 2) / 2;
        }
        WriteLine($"! {left}");
    }
}