#include <iostream>
#include <algorithm>
#include <functional>
#include <string>
#include <climits>
#include <vector>
#include <numeric>
#include <complex>
#include <map>
#include <bitset>
using namespace std;

//#define __int64 long long
//#define long __int64
#define REP(i,a,b) for(int i=a;i<b;i++)
#define rep(i,n) REP(i,0,n)
const int Vecy[4] = {0,-1,0,1};
const int Vecx[4] = {1,0,-1,0};


int main(){
	int ans;
	int mind = 0;
	int maxd = 10000000001;
	int check;
	int result;
	
	int i = 0;
	cout << "? " << 100 << endl;
	cin >> result;
	if(result == 0){
		cout << "! 100" << endl;
		return 0;
	}
	
	if(result == -1){
		//100以下用
		mind = 0;
		maxd = 100;
		
		for(i=1; i<100; i++){
			check = (mind + maxd) / 2;
			cout << "? " << (check - i) << endl;
			cin >> result;
			if(result == 0){
				break;
			}
			if(result == -1){
				maxd = check;
			}else{
				mind = check;
			}
		}
		cout << "! " << check << endl;
	    return 0;
	}
	
	
	for(i=1; i<100; i++){
		check = (mind + maxd) / 2;
		cout << "? " << (check - i) << endl;
		cin >> result;
		if(result == 0){
			break;
		}
		if(result == -1){
			maxd = check;
		}else{
			mind = check;
		}
	}
	cout << "! " << check << endl;
	
    return 0;
}