#include <bits/stdc++.h>
#define rep(i, a) for (int i = 0; i < (a); i++)
#define rep2(i, a, b) for (int i = (a); i < (b); i++)
#define repr(i, a) for (int i = (a) - 1; i >= 0; i--)
#define repr2(i, a, b) for (int i = (b) - 1; i >= (a); i--)
#define itall(a) a.begin(), a.end()
using namespace std;
typedef long long ll;
const ll inf = 1e9;
const ll mod = 1e9 + 7;
const double pi = acos(-1);
const double eps = 1e-8;
template<typename T> inline T sq(T a) { return a * a; }
template<typename T> inline T cb(T a) { return a * a * a; }
template<typename T> inline bool umin(T &a, const T &b) { return b < a && (a = b, true); }
template<typename T> inline bool umax(T &a, const T &b) { return a < b && (a = b, true); }

ll p10[10];

int query(int x) {
    cout << "? " << x << endl;
    int res;
    cin >> res;
    return res;
}

int main() {
    int ans = 0;

    if (query(99) < 0) {
        rep (i, 99) {
            if (query(0) == 0) {
                ans = 1 + i;
                break;
            }
        }
    } else {
        int l = 10, r = 1e9 + 1;
        for (int i = 0; r - l > 1 && i < 100; i++) {
            int m = (l + r) / 2;

            int q = query(m - i - 1);

            if (q == 0) {
                ans = m;
                break;
            } else if (q > 0) {
                l = m;
            } else {
                r = m;
            }
        }
    }

    cout << "! " << ans << endl;
}