#include <bits/stdc++.h>
using namespace std;

// 基本テンプレート
struct cww{cww(){ios::sync_with_stdio(false);cin.tie(0);}}star;
#define P(x) cout << (x) << endl
#define p(x) cout << (x)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define MAT(type, c, m, n) vector<vector<type>> c(m, vector<type>(n));for(auto& r:c)for(auto& i:r)cin>>i;
#define VV(type, c, m, n, i) vector<vector<type>> c(m, vector<type>(n, i));
#define REP(i,a,n) for(int i=(a), i##_len=(n); i<i##_len; ++i)
#define RREP(i,a,n) for(int i=(a); i>n; --i)
#define perm(c) sort(ALL(c));for(bool c##p=1;c##p;c##p=next_permutation(ALL(c)))
#define cauto const auto&
#define UNIQUE(v) v.erase( unique(ALL(v)), v.end() );
#define len(x) ((int)(x).size())
#define GET_ARRAY_SIZE(a)   (sizeof(a)/sizeof(a[0]))
void print() {}
template <class H, class... T> void print(H h, T... t){P(h);print(t...);}


// 型
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<string, string> pss;
typedef pair<string, int> psi;
typedef pair<int, string> pis;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector<long long> vll;
typedef vector<string> vs;

// 4近傍
//int dy[]={0, 1, 0, -1};
//int dx[]={1, 0, -1, 0};

// 8近傍
//int dy[]={0,0,1,-1,1,1,-1,-1};
//int dx[]={1,-1,0,0,1,-1,1,-1};
//constexpr int dx[]={-2, -2, -1, -1, 1, 1, 2, 2};
//constexpr int dy[]={-1, 1, -2, 2, -2, 2, -1, 1};

 ll mod = (int)1e9 + 7;

// 定数
#define PI acos(-1.0)
constexpr int EPS = (1e-9);
constexpr int INF = 100000000;

//constexpr ll MAX = 1000000000;


int main() {
//	cout << setprecision(10) << fixed;

	int min = 1, mid, max = 1e9;

	while(min != max) {
		mid = (min + max) / 2;

		cout << "? " << mid << endl;

		int res; cin >> res;
		if (res) min = mid;
		else max = mid;
	}
	cout << "! " << min << endl;

	return 0;
}