#include <iostream>

void solve() {
    int ok = 1, ng = 1000000001;
    while (ng - ok > 1) {
        int mid = (ok + ng) / 2;
        std::cout << "? " << mid << std::endl;

        int c;
        std::cin >> c;
        if (c) {
            ok = mid;
        } else {
            ng = mid;
        }
    }

    std::cout << "! " << ok << std::endl;
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}