#ifdef __GNUC__
#pragma GCC optimize ("O3")
#pragma GCC target ("avx")
#endif

#define _USE_MATH_DEFINES

#include <iostream>
#include <iomanip>
#include <stdio.h>

#include <sstream>
#include <algorithm>
#include <cmath>

#include <string>
#include <cstring>
#include <vector>
#include <valarray>
#include <array>

#include <queue>
#include <complex>
#include <set>
#include <map>
#include <stack>
#include <list>

#include <cassert>//assert();
#include <fstream>
/////////
#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i,n) REP(i,0,n)

/////////
typedef long long LL;
typedef long double LD;
typedef unsigned long long ULL;
#define PII pair<int,int>
/////////
using namespace::std;

// 最大公約数
template<class T>
inline T gcd(T a, T b){return b == 0 ? a : gcd(b, a % b);}
// 最小公倍数
template<class T>
inline T lcm(T a, T b){return a * b / gcd(a, b);}
////////////////////////////////

inline void solve(){
	//10以上10**9以下
	int res;
	int left,right,cen;
	cen = 512;
	cout << "?" << cen << endl;
	cin >> res;
	if( res < 0 ){
		left = 10;
		right = cen;
	}else if( res > 0 ){
		left = cen;
		right = 1000000001;
	}else{//res == 0
		cout << "!" << cen << endl;
		exit(0);
	}
	int turn = 1;
	while(1){
		--left;
		--right;
		cen = (left+right)/2;
		cout << "?" << cen << endl;
		cin >> res;
		if( res < 0 ){
			right = cen;
		}else if(0 < res){
			left = cen;
		}else{
			cout << "!" << cen + turn << endl;
			exit(0);
		}
		++turn;
	}
}

int main(void){
	std::cin.tie(0);
	std::ios::sync_with_stdio(false);
	//std::cout << std::fixed;//小数を10進数表示
	//cout << setprecision(16);//小数をいっぱい表示する。16?

	solve();

	return 0;
}