#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for(ll i = 0, i##_len = (n); i < i##_len; i++)
#define reps(i, s, n) for(ll i = (s), i##_len = (n); i < i##_len; i++)
#define rrep(i, n) for(ll i = (n) - 1; i >= 0; i--)
#define rreps(i, e, n) for(ll i = (n) - 1; i >= (e); i--)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) ((ll)(x).size())
#define len(x) ((ll)(x).length())
#define endl "\n"

int main() {
    ll low = 0, high = 1e9 + 1;
    while((low + 1) < high) {
        ll mid = (low + high) / 2;
        cout << "? " << mid << endl;
        ll ans;
        cin >> ans;
        if (ans == 1) {
            low = mid;
        }
        else {
            high = mid;
        }
    }
    cout << "! " << low << endl;
    return 0;
}