#include<iostream>
#include<iomanip>
#include<string>
#include<algorithm>
#include<vector>
#include<set>
#include<list>
#include<queue>
#include<math.h>
#include<bitset>
using ll = long long;
using namespace std;

int main(){
    int low = 1, hi = 1e9+1, mid = (low + hi) / 2, q = -1, pq = -1;
    cout << "? " << mid << endl; 
    while (mid != low){
        cin >> q;
        if (q == 1) low = mid;
        else hi = mid;
        mid = (low + hi)/ 2;
        pq = q;
        cout << "? " << mid << endl;
    }
    cout << "! " << low << endl;
}