#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(ll i=0;i<n;i++)
#define srep(i,l,r) for(ll i=l;i<=r;i++)
#define irep(i,r,l) for(ll i=r;i>=l;i--)
using ll = long long;
using ld = long double;
const ll mod=998244353;
#define vout(v) for(auto i :v) cout<<i<<" ";
#define INF 9223300000000000000ll
#define Winf 5e12
#define nl "\n"
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define vl vector<ll>
#define pb push_back
#define vc vector<char>


void no() { cout<<"No"<<nl;}
void yes() { cout<<"Yes"<<nl;}
void yn(bool a) {
    cout<<(a ? "Yes":"No")<<nl;
}



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


int main() {
    ll lef=1,rig=1000001;
    ll prev=0,ask;
    cout<<"? 0"<<endl;
    while(rig-lef>1) {
        ll mid=(rig-lef)/2+lef;
        ask=2*mid-prev-1;
        cout<<"? "<<ask<<endl;
        int ans; cin>>ans;
        if(bool(ans)==(ask>=prev)) lef=mid;
        else rig=mid;
        prev=ask;
    }
    cout<<"! "<<lef<<nl;
}