#include <bits/stdc++.h>
using namespace std;

#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define repi(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define all(x) (x).begin(),(x).end()
#define foreach(u,v) for(auto (u) : (v))
#define pb push_back
#define mp make_pair
#define mt make_tuple

typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<ll, ll> pll;
typedef vector<ll> vl;

const int inf = 1e9;
const ll linf = 1LL<<60;
const ll mod = 1e9 + 7;
const double eps = 1e-9;

/*{
}*/

int main()
{
  int l = 0, r = 1e9;
  while(r-l > 1){
    int m = (l+r) / 2;
    cout << "? " << m << endl;
    
    int f;
    cin >> f;

    if(f){
      l = m;
    }else{
      r = m;
    }
  }

  cout << "! " << l << endl;

  return 0;
}