/* 
 * File:   main.cpp
 * Author: VirtualDemon
 *
 * Created on April 11, 2010, 3:51 PM
 */
#include <vector>
#include <cstdlib>
#include <fstream>
#include <iomanip>
#include <iterator>
#include <algorithm>

/*
 *
 */
using namespace std;
class pr
{
public:
    double x, y;
    pr( void ) : x(0.00), y(0.00) { }
    pr( double _x, double _y ) : x(_x), y(_y) { }
    inline bool operator<( const pr& z ) const;
    friend inline istream& operator>>( istream& in, pr& x )
    {
        in>>x.x>>x.y;
        return in;
    }
    friend inline ostream& operator<<( ostream& out, const pr& x )
    {
        out<<fixed<<setprecision(12)<<x.x<<' '<<x.y<<'\n';
        return out;
    }
} p0, p;
vector< pr > v, ConvexHull;
inline bool pr::operator <(const pr& z) const
{
     return ( x - p0.x )*( z.y - p0.y ) < ( z.x - p0.x )*( y-p0.y );
}
inline bool cmp( const pr& p0, const pr& p, const pr& p2 )
{
    return ( p0.x*p.y + p.x*p2.y + p0.y*p2.x ) >= ( p.y*p2.x + p2.y*p0.x + p.x*p0.y );
}
int main( void )
{
    int N, i, j;
    ifstream in( "infasuratoare.in" );
    in>>N>>p0;
    for( i=1; i < N; ++i )
    {
        in>>p;
        if( p.y < p0.y || ( p.y == p0.y && p.x < p0.x ) )
        {
            v.push_back(p0);
            p0=p;
            continue;
        }
        v.push_back(p);
    }
    sort( v.begin(), v.end() );
    ConvexHull.push_back(p0);
    ConvexHull.push_back(v[0]);
    ConvexHull.push_back(v[1]);
    for( i=2, N-=1; i < N; ++i )
    {
        for( j=ConvexHull.size(); j >= 2 && cmp( ConvexHull[j-2], ConvexHull[j-1], v[i] ); --j )
            ConvexHull.pop_back();
        ConvexHull.push_back(v[i]);
    }
    ofstream out( "infasuratoare.out" );
    out<<ConvexHull.size()<<'\n';
    copy( ConvexHull.begin(), ConvexHull.end(), ostream_iterator<pr>( out ) );
    return EXIT_SUCCESS;
}