#include <cstdio>
#include <iostream>
#include <algorithm>
#include <complex>
#include <queue>
#include <map>
using namespace std;

#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define FORR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n) for (int i=0;i<(n);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#define pb push_back
#define ALL(a) (a).begin(),(a).end()

#define EPS (1e-10)
#define EQ(a,b) (abs((a)-(b)) < EPS)

#define PI 3.1415926535

typedef long long ll;
//typedef pair<int, int> P;
//typedef complex<double> C;

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

void ans(int Y) {
    cout << "! " << Y << endl;
}

void solve() {
    // 質問回数(ろうそくの減った長さ)
    int cnt = 0;

    // L < Y となるまでYを増やす
    ll Y = 10;
    while (true) {
        int query = ask(Y);
        if (query == 0) {
            // L == Y
            ans(Y + cnt);
            return;
        } else if (query == -1) {
            // L < Y
            break;
        }
        Y *= 2;
        cnt++;
    }
    cnt++;

    int ok = 0;
    int ng = Y;
    while (true) {
        int mid = (ok + ng) / 2;
        int query = ask(mid);
        if (query == 0) {
            // L == Y
            ans(mid + cnt);
            return;
        } else if (query == 1) {
            // L > Y
            ok = mid;
        } else {
            ng = mid;
        }
        ok = max(0, ok - 1);
        ng--;
        cnt++;
    }

}

int main() {
    // input();
    solve();
    return 0;
}