#include <bits/stdc++.h>

using namespace std;

namespace {

    typedef double real;
    typedef long long ll;

    template<class T> ostream& operator<<(ostream& os, const vector<T>& vs) {
        if (vs.empty()) return os << "[]";
        auto i = vs.begin();
        os << "[" << *i;
        for (++i; i != vs.end(); ++i) os << " " << *i;
        return os << "]";
    }
    template<class T> istream& operator>>(istream& is, vector<T>& vs) {
        for (auto it = vs.begin(); it != vs.end(); it++) is >> *it;
        return is;
    }

    void input() {
    }

    void solve() {
        cout << "? 100" << endl;
        int y; cin >> y;
        if (y == 0) {
            cout << "! 100" << endl;
            return;
        } else if (y > 0) {
            // do nothing
        } else {
            assert(y < 0);
            for (int t = 1; ; t++) {
                cout << "? 0" << endl;
                int y; cin >> y;
                if (y == 0) {
                    cout << "! " << t << endl;
                    return;
                }
            }
        }
        int lb = 10, ub = int(1e9) + 1;
        for (int t = 1; ; t++) {
            int mid = lb + (ub - lb) / 2;
            cout << "? " << mid << endl;
            int y; cin >> y;
            if (y < 0) {
                lb = max(0, lb - 1);
                ub = mid;
            } else if (y == 0) {
                cout << "! " << mid + t << endl;
                return;
            } else {
                assert(y > 0);
                lb = max(0, mid - 1);
                ub--;
            }
        }
    }
}

int main() {
    input(); solve();
    return 0;
}