#include <bits/stdc++.h>

using namespace std;
using ll = long long;

#ifdef LOCAL
#include "debug.h"
#else
#define dbg(...) 0
#define dbgn(...) 0
#endif

int q(ll x) {
    cout << "? " << x << endl;
    int response;
    cin >> response;
    if (response == -1) {
        exit(0);
    }
    return response;
}

int32_t main() {
    cin.tie(0)->sync_with_stdio(0);
    ll l = 1, r = 1000000;
    ll prev_x, curr_x;
    int resp;
    prev_x = 1;
    cout << "? " << prev_x << endl;
    curr_x = 1000000;
    resp = q(curr_x);
    if (resp == 1) {
        l = 500001;
    } else {
        r = 500000;
    }
    prev_x = curr_x;
    while (l < r) {
        ll m;
        if (prev_x > r) {
            m = l + (r - l) / 2;
        } else {
            m = l + (r - l + 1) / 2;
        }
        curr_x = 2 * m - prev_x;
        resp = q(curr_x);
        if (curr_x > prev_x) {
            if (resp == 1) {
                l = m;
            } else {
                r = m - 1;
            }
        } else {
            if (resp == 1) {
                r = m;
            } else {
                l = m + 1;
            }
        }
        prev_x = curr_x;
    }
    cout << "! " << l << endl; 
    return 0;
}