#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;

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

int main(){
    int L = 0, R = 1000000001;
    while(R - L > 1){
        int M = (L + R) / 2;
        (ask(M) >= 0 ? L : R) = M;
        L = max(0, L - 1);
        R = max(1, R - 1);
    }
    cout << "! " << L << endl;
    return 0;
}