//https://ncode.syosetu.com/n4830bu/246/
#include <bits/stdc++.h>
using namespace std;

int main() {
    int ok = 0;
    int ng = 1e9 + 10;
    auto check = [](int x) {
        cout << "? " << x << endl;
        int res;
        cin >> res;
        return res;
    };
    while (abs(ok - ng) > 1) {
        int mid = (ok + ng) / 2;
        if (check(mid)) {
            ok = mid;
        } else {
            ng = mid;
        }
    }
    cout << "! " << ok << endl;
}