// No.246 質問と回答
// https://yukicoder.me/problems/no/246
//
#include <iostream>
using namespace std;

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

    int ub = 1000000000;
    int lb = 1;

    while (ub > lb + 4) {
        int mid = (ub + lb) / 2;
        cout << "? " << mid << flush << endl;
        int res;
        cin >> res;
        if (res == 0)
            ub = mid;
        else
            lb = mid;
    }

    for (int i = lb; i <= ub+1; ++i) {
        cout << "? " << i << flush << endl;
        int res;
        cin >> res;
        if (res == 0) {
            cout << "! " << i - 1 << flush << endl;
            break;
        }
    }
}