#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;

#define rep(i,n) for(ll i=0;i<n;++i)
#define all(a) (a).begin(),(a).end()
ll intpow(ll a, ll b){ ll ans = 1; while(b){ if(b & 1) ans *= a; a *= a; b /= 2; } return ans; }
ll modpow(ll a, ll b, ll p){ ll ans = 1; while(b){ if(b & 1) (ans *= a) %= p; (a *= a) %= p; b /= 2; } return ans; }
template<class T> T div_floor(T a, T b) { return a / b - ((a ^ b) < 0 && a % b); }
template<class T> T div_ceil(T a, T b) { return a / b + ((a ^ b) > 0 && a % b); }
template <typename T, typename U> inline bool chmin(T &x, U y) { return (y < x) ? (x = y, true) : false; }
template <typename T, typename U> inline bool chmax(T &x, U y) { return (x < y) ? (x = y, true) : false; }


void solve() {
    ll ans=459;
    ll before=0;
    auto query=[&](ll x)->ll {
        cout<<"? "<<x<<endl;
        ll res;
        cin>>res;
        // if (abs(before-ans)>=abs(x-ans)){
        //     res=1;
        // }
        // else res=0;
        before=x;
        return res;
    };
    cout<<"? "<<before<<endl;
    ll ng=0;
    ll ok=1e6+20;
    while (ok-ng>1){
        ll mid=(ok+ng)/2;
        if (before<=mid){
            ll x=2*mid-before+1;
            ll res=query(x);
            if (res==1){
                ng=mid;
            }
            else{
                ok=mid;
            }
        }
        else{
            ll x=2*mid-before;
            ll res=query(x);
            if (res==1){
                ok=mid;
            }
            else{
                ng=mid;
            }
        }
    }
    cout<<"! "<<ok<<endl;
    return;
}


int main() {
    ll T=1;
    while (T--){
        solve();
    }
    return 0;
}