// Include
#include <fstream>
#include <iomanip>
#include <utility>
#include <vector>
#include <algorithm>
using namespace std;

// Definitii
#define point_t pair<double, double>
#define y first
#define x second

#define pb push_back
#define popb pop_back

#define prev at(convexHull.size()-2)
#define top at(convexHull.size()-1)

#define leftTurn(a, b, c) (det(a, b, c) > 0)

// Constante
const int sz = (int)12e4+1;

// Functii
double det(point_t a, point_t b, point_t c);
class byAngle
{
	public:
	bool operator()(point_t a, point_t b);
};

// Variabile
ifstream in("infasuratoare.in");
ofstream out("infasuratoare.out");

int num;

point_t minPoint;

point_t points[sz];

vector<point_t> convexHull;

// Main
int main()
{
	out << fixed << setprecision(6);
	in >> num;
	in >> minPoint.x >> minPoint.y;
	
	for(int i=1 ; i<num ; ++i)
	{
		in >> points[i].x >> points[i].y;
		if(points[i] < minPoint)
			swap(points[i], minPoint);
	}
	
	sort(points+1, points+num, byAngle());
	
	convexHull.pb(minPoint);
	convexHull.pb(points[1]);
	
	for(int i=2 ; i<num ; ++i)
	{
		while(!leftTurn(convexHull.prev, convexHull.top, points[i]))
			convexHull.popb();
		convexHull.pb(points[i]);
	}
	
	out << convexHull.size() << '\n';
	
	vector<point_t>::iterator it, end=convexHull.end();
	for(it=convexHull.begin() ; it!=end ; ++it)
		out << it->x << ' ' << it->y << '\n';
	
	in.close();
	out.close();
	return 0;
}


double det(point_t a, point_t b, point_t c)
{   return a.x*b.y + b.x*c.y + c.x*a.y - a.y*b.x - b.y*c.x - c.y*a.x;   }

bool byAngle::operator() (point_t a, point_t b)
{	return leftTurn(minPoint, a, b);	}