#include <iostream>
#include <algorithm>
#include <iomanip>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <bitset>
#include <cmath>

static const int MOD = 1000000007;
using ll = long long;
using u32 = uint32_t;
using namespace std;

template<class T> constexpr T INF = ::numeric_limits<T>::max() / 32 * 15 + 208;

int main() {
    int t = 8;
    int a = 0;
    while(true){
        cout << "? " << max(t-a, 0) << endl;
        a++;
        int x; cin >> x;
        if(!x) {
            cout << "! " << t << "\n";
            return 0;
        }
        if(x < 0) break;
        t *= 2;
       
    }
    int ok = t/2, ng = t;
    while(ng-ok > 1){
        int mid = (ok+ng)/2;
        cout << "? " << max(mid-a, 0) << endl;
        int x; cin >> x;
        if(!x) {
            cout << "! " << mid << endl;
            return 0;
        }
        (x == 1 ? ok : ng) = mid;
        a++;
    }
    cout << "! " << ok << endl;
    return 0;
}