#include <bits/stdc++.h>

using namespace std;


typedef int32_t h_int32;
typedef int64_t h_int64;
typedef uint32_t uh_int32;
typedef uint64_t uh_int64;
typedef h_int64 h_int;

#define REP( i, n ) for(int i = 0; i < ( int )( n ); ++i )
#define REPR( i, n ) for(int i = ( int )( n ); i >= 0; --i )
#define FOR( i, a, n ) for(int i = ( int )( a ); i < ( int )( n ); ++i )
#define FORR( i, a, n ) for(int i = ( int )( n ); i >= ( int )( a ); --i)

#define ALL( x ) x.begin(), x.end()

#define DOUT( x ) cerr << #x << " = " << x << "\n"
#define COUT( x ) cout << ( x ) << "\n"
#define DOUBLECOUT( num, x ) cout << fixed << setprecision( num ) << ( x ) << "\n"

#define INF 999999999
#define PI 3.14159265359

bool Question( h_int num )
{
        cout << "? " << num << endl;
        int n;
        cin >> n;
        return n == 1;
}

signed main()
{
        ios::sync_with_stdio( false );
        cin.tie( 0 );

        h_int l = 0;
        h_int r = 1000000000;
        while(r - l > 1)
        {
                h_int m = ( l + r ) / 2;
                if( Question( m ) )
                {
                        l = m;
                }
                else
                {
                        r = m;
                }
        }
        if( Question( r ) )
        {
                cout << "! " << r << endl;
        }
        else
        {
                cout << "! " << l << endl;
        }
        return 0;
}