using System;
using System.Collections;
using System.Collections.Generic;
 
class TEST{
	static void Main(){
		Sol mySol =new Sol();
		mySol.Solve();
	}
}

class Sol{
	public void Solve(){
		
		int l=1;
		int r=(int)1e9;
		int c=0;
		while(r-l>1){
			c=(r+l)/2;
			Console.WriteLine("? {0}",c);
			var res=ri();
			if(res==1){
				l=c;
			}else{
				r=c;
			}
		}
		
		while(true){
			Console.WriteLine("? {0}",c);
			var res=ri();
			if(res!=1){c--;continue;}
			break;
		}
		while(true){
			Console.WriteLine("? {0}",c);
			var res=ri();
			if(res==1){c++;continue;}
			break;
		}
		Console.WriteLine("! {0}",c-1);
		
		
	}

	public Sol(){
	}




	static String rs(){return Console.ReadLine();}
	static int ri(){return int.Parse(Console.ReadLine());}
	static long rl(){return long.Parse(Console.ReadLine());}
	static double rd(){return double.Parse(Console.ReadLine());}
	static String[] rsa(){return Console.ReadLine().Split(' ');}
	static int[] ria(){return Array.ConvertAll(Console.ReadLine().Split(' '),e=>int.Parse(e));}
	static long[] rla(){return Array.ConvertAll(Console.ReadLine().Split(' '),e=>long.Parse(e));}
	static double[] rda(){return Array.ConvertAll(Console.ReadLine().Split(' '),e=>double.Parse(e));}
}