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

#define REP(i, n) for(int i=0; i<(n); i++)

int cnt = 0;
int ask(int Y){
    cout << "? " << Y << endl;
    int res;
    cin >> res;
    cnt++;
    return res;
}
signed main()
{
    int high = (int)1e9;
    int low = 10;
    int c10 = 20;
    REP(i,100) {
        if (cnt % 10 == 0) {
            int ret10 = ask(c10);
            if (ret10 == 0) {
                cout << "! " << c10 + cnt - 1 << endl;
                return 0;
            }
            if (ret10 == -1) {
                high = c10;
                low = 0;
            }
        }
        int mid = (high + low) / 2;
        int ret = ask(mid);
        if (ret == 0) {
            cout << "! " << mid + cnt - 1 << endl;
            return 0;
        }
        if (ret == 1) {
            low = mid;
        } else {
            high = mid;
        }
        high = max(0, high-1);
        low = max(0, low-1);
    }
    return 0;
}