#include <bits/stdc++.h>
using namespace std;
using i64 = int64_t;
using vi = vector<i64>;
using vvi = vector<vi>;

int main() {
    int l = 1, r = 1e9;
    cout << "? " << r << endl;
    int res;
    cin >> res;
    if (res == 1) {
        cout << "! " << r << endl;
        return 0;
    }
    while (l < r - 1) {
        int m = (l + r) / 2;
        cout << "? " << m << endl;
        cin >> res;
        if (res) {
            l = m;
        } else {
            r = m;
        }
    }
    cout << "! " << l << endl;
}