#if !__INCLUDE_LEVEL__

#include __FILE__

/*
（目的値）～正の無限 が条件を満たす場合
ng…条件を満たさない値の範囲での最大値
ok…条件を満たす値の範囲での最小値
ng < ok
is_ok == Trueの場合、探索範囲が左半分へ
is_ok == Falseの場合、探索範囲が右半分へ
*/

int main()
{
    ll ok = 0;
    ll ng = 1000000001;
    while (abs(ng - ok) > 1) {
        ll mid = (ok + ng) / 2;
        int is_ok = 0;
        cout << "?" << " " << mid << endl;
        cin >> is_ok;
        if (is_ok) {
            ok = mid;
        } else {
            ng = mid;
        }
    }
    cout << "!" << " " << ok << endl;
}

#else

#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i, n) for(int i = 0; i < n; i++)
#define rrep(i, n) for(int i = n-1; i >= 0; i--)
#define range(i, m, n) for(int i = m; i < n; i++)
#define fore(i,a) for(auto &i:a)
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define Sum(v) accumulate(all(v),ll(0))
#define minv(v) *min_element(all(v))
#define maxv(v) *max_element(all(v))
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vector<ll>> vvl;
const ll INF = 1e16;
const ll MOD1 = 1000000007;
const ll MOD2 = 998244353;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
ll SN(char s){return ll(s-'0');}
ll SN(string s){return stoll(s);}
int alpN(char s){return int(s-'a');}
int AlpN(char s){return int(s-'A');}
using Graph = vector<vector<ll>>;
using GraphCost = vector<vector<pair<ll,ll>>>;
using mint1 = modint1000000007;
using mint2 = modint998244353;
using pll = pair<long long, long long>;
template <class T>ostream &operator<<(ostream &o,const vector<T>&v){for(int i=0;i<(int)v.size();i++)o<<(i>0?" ":"")<<v[i];return o;}//vector空白区切り出力
ostream& operator<<(ostream& os, const mint1& N) {return os << N.val();}//mint出力。デフォはmint1
ostream& operator<<(ostream& os, const mint2& N) {return os << N.val();}
template<class T> bool contain(const std::string& s, const T& v) {
    return s.find(v) != std::string::npos;
}
ll max(int x,ll y){return max((ll)x,y);}
ll max(ll x,int y){return max(x,(ll)y);}
ll min(int x,ll y){return min((ll)x,y);}
ll min(ll x,int y){return min(x,(ll)y);}

#endif