//https://ncode.syosetu.com/n4830bu/253/
#include <bits/stdc++.h>
using namespace std;

int Time = -1;

int ask(int Y) {
    Time++;
    cout << "? " << Y << endl;
    int res;
    cin >> res;
    return res;
}

int main() {
    int res = ask(100);
    if (res == 0)
        cout << "! 100" << endl;
    else if (res < 0) {
        while (res != 0)
            res = ask(1);
        cout << "! " << Time + 1 << endl;
    } else {
        int ok = 1e9 + 10;
        int ng = 0;
        while (abs(ok - ng) > 1) {
            int mid = (ok + ng) / 2;
            res = ask(mid - Time);
            if (res == 0) {
                ok = mid;
                break;
            }
            if (res == -1) {
                ok = mid;
            } else {
                ng = mid;
            }
        }
        cout << "! " << ok + 1 << endl;
    }
}