using System;

namespace No253{
    public class Program{
        public static void Main(string[] args){
            Func<int, int> ask = x =>{
                Console.WriteLine($"? {x}");
                return int.Parse(Console.ReadLine().Split(' ')[0]);
            };


            var t = ask(30);
            if(t == 0){
                Console.WriteLine($"! 30");
                return;
            }

            if(t == -1){
                var i = 0;
                for(; i < 30; i++){
                    if(ask(0) == 0) break;
                }
                Console.WriteLine($"! {i + 1}");
                return;
            }

            if(t == 1){
                var left = 0;
                var right = 1000000001;
                var cnt = 1;

                while(left < right){
                    cnt++;
                    var mid = (left + right) / 2;
                    var quest = ask(mid - cnt);
                    if(quest == 0){
                        left = mid;
                        break;
                    }
                    if(quest == -1){
                        right = mid;
                    }
                    if(quest == 1){
                        left = mid + 1;
                    }
                }

                Console.WriteLine($"! {left - 1}");
                return;
            }
        }
    }
}