#include <vector>
#include <fstream>
#include <iomanip>
#include <cstdlib>
#include <iterator>
#include <algorithm>
#define N_MAX 120011
#define oo 1<<28

using namespace std;
struct vertex
{
	double x, y;
	vertex() : x(0), y(0) { }
	vertex( double _x, double _y ) : x(_x), y(_y) { }
} p0, p;
vector< vertex > v, ConvexHull;
inline bool operator<( const vertex& z1, const vertex& z2 )
{
	return (z1.x-p0.x)*(z2.y-p0.y) < (z1.y-p0.y)*(z2.x-p0.x);
}
inline bool cmp( const vertex& p0, const vertex& p1, const vertex& p2 )
{
	return ( p0.x*p1.y+p1.x*p2.y+p0.y*p2.x ) >= ( p1.y*p2.x+p2.y*p0.x+p1.x*p0.y ) ;
}
inline istream& operator>>( istream& in, vertex& p )
{
	in>>p.x>>p.y;
	return in;
}
inline ostream& operator<<( ostream& out, const vertex& p )
{
	out<<fixed<<setprecision(8)<<p.x<<' '<<p.y;
	return out;
}
int main( void )
{
	int N, i, j;
	ifstream in( "infasuratoare.in" );
	in>>N>>p0;
	for( i=2; i <= N; ++i )
	{
		in>>p;
		if( ( p0.x == p.x && p0.y > p.y ) || p0.x > p.x )
		{
			v.push_back(p0);
			p0=p;
		}
		else 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()-1; j >= 1 && cmp( ConvexHull[j-1], ConvexHull[j], v[i] ); --j )
			ConvexHull.pop_back();
		ConvexHull.push_back(v[i]);
	}
	ofstream out( "infasuratoare.out" );
	out<<ConvexHull.size()<<'\n';
	copy( ConvexHull.rbegin(), ConvexHull.rend(), ostream_iterator<vertex>( out, "\n" ) );
	return EXIT_SUCCESS;
}