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

using std::cin;
using std::cout;

#define rep(i,n) for(int i = 0; i < (int)n; i++)
#define FOR(n) for(int i = 0; i < (int)n; i++)
#define repi(i,a,b) for(int i = (int)a; i < (int)b; i++)
#define all(x) x.begin(),x.end()
//#define mp make_pair
#define vi vector<int>
#define vvi vector<vi>
#define vvvi vector<vvi>
#define vvvvi vector<vvvi>
#define pii pair<int,int>
#define vpii vector<pair<int,int>>

template<typename T>
bool chmax(T &a, const T b) {if(a<b) {a=b; return true;} else {return false;}}
template<typename T>
bool chmin(T &a, const T b) {if(a>b) {a=b; return true;} else {return false;}}

using ll = long long;
using ld = long double;
using ull = unsigned long long;

const ll INF = numeric_limits<long long>::max() / 2;
const ld pi = 3.1415926535897932384626433832795028;
const ll mod = 998244353;
int dx[] = {1, 0, -1, 0, -1, -1, 1, 1};
int dy[] = {0, 1, 0, -1, -1, 1, -1, 1};

#define int long long

void solve() {
    vi xs;
    auto ask = [&](int x) -> int {
        // assert((int)xs.size() < 25);
        cout << "? " << x << endl;
        cout << flush;
        xs.emplace_back(x);
        if ((int)xs.size() == 1) return -1;
        int ret;
        cin >> ret;
        return ret;
    };
    auto answer = [&](int x) -> void {
        cout << "! " << x << endl;
        cout << flush;
        exit(0);
    };
    int l = 1, r = 1e6;
    ask(-1e7);
    int which = 1;
    while (r - l > 1) {
        int mid = (l + r) >> 1;
        if (which) {
            int ans = ask(1e7 + 1e6 + 2 * (mid - 5e5));
            if (ans == 1) l = mid;
            else r = mid;
        } else {
            int ans = ask(-1e7 + 2 * (5e5 - mid));
            if (ans == 1) r = mid;
            else l = mid;
        }
        which ^= 1;
    }
    ask(l);
    int ret = ask(r);
    if (ret == 1) answer(r);
    else answer(l);
}

signed main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    solve();
    return 0;
}