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

typedef long long ll;
typedef vector< int > vi;
typedef vector< vi > vvi;
typedef vector< ll > vl;
typedef vector< vl > vvl;
typedef pair< int, int > pii;
typedef vector< pii > vp;
typedef vector< double > vd;
typedef vector< vd > vvd;
typedef vector< string > vs;

template< class T1, class T2 >
int upmin( T1 &x, T2 v ){
  if( x > v ){
    x = v;
    return 1;
  }
  return 0;
}

template< class T1, class T2 >
int upmax( T1 &x, T2 v ){
  if( x < v ){
    x = v;
    return 1;
  }
  return 0;
}

const int INF = 0x3f3f3f3f;

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

void init(){

}

void preprocess(){
  int ans = INF;
  int v = ask( 200 );
  if( v < 0 ){
    int lb = 1, rb = 199;
    int turn = 1;
    while( lb <= rb ){
      int mid = lb + rb >> 1;
      int u = ask( mid - turn );
      if( u == 0 ){
        ans = mid;
        break;
      }
      if( u < 0 )
        rb = mid - 1;
      else
        lb = mid + 1;
      ++turn;
    }
  } else if( v > 0 ){
    int lb = 201, rb = ( int ) 1e9;
    int turn = 1;
    while( lb <= rb ){
      int mid = lb + rb >> 1;
      int u = ask( mid - turn );
      if( u == 0 ){
        ans = mid;
        break;
      }
      if( u < 0 )
        rb = mid - 1;
      else
        lb = mid + 1;
      ++turn;
    }
  } else{
    ans = v;
  }
  cout << "! " << ans << endl;
}

void solve(){

}

signed main(){
  ios::sync_with_stdio( 0 );
  init();
  preprocess();
  solve();
  return 0;
}