#include <bits/stdc++.h>
using namespace std;

int main() {
    int L = 1, R = 1000000;

    long long prev = 1;
    cout << "? " << prev << endl;
    cout.flush();

    while (L < R) {
        int mid = (L + R) / 2;

        long long x = 2LL * mid + 1 - prev;

        cout << "? " << x << endl;
        cout.flush();

        int res;
        cin >> res;
        if (res == -1) return 0;

        if (x > prev) {
            // res = 1 <=> |a-prev| >= |a-x|
            //         <=> a >= mid + 1
            if (res == 1) {
                L = mid + 1;
            } else {
                R = mid;
            }
        } else {
            // x < prev のときは向きが逆
            // res = 1 <=> a <= mid
            if (res == 1) {
                R = mid;
            } else {
                L = mid + 1;
            }
        }

        prev = x;
    }

    cout << "! " << L << endl;
    cout.flush();

    return 0;
}