#include <cstdio>
#include <algorithm>
#include <utility>
#include <vector>
#include <cmath>

typedef std::pair<double,double> Point;
typedef std::vector<Point> Polygon;

const int MAX_SIZE(120001);
const double GUARD(0.00000001);

Polygon Hull;
std::vector<Point> Points;
Point Stack [MAX_SIZE];

inline void Read (void)
{
	std::freopen("infasuratoare.in","r",stdin);
	double x, y;
	int n;
	std::scanf("%d",&n);
	for (int counter(0) ; counter < n ; ++counter)
	{
		std::scanf("%lf %lf",&x,&y);
		Points.push_back(std::make_pair(x,y));
	}
	std::fclose(stdin);
}

inline void Print (void)
{
	std::freopen("infasuratoare.out","w",stdout);
	std::printf("%lu\n",Hull.size());
	for (int index(0), end(Hull.size()) ; index < end ; ++index)
		std::printf("%.9lf %.9lf\n",Hull[index].first,Hull[index].second);
	std::fclose(stdout);
}

inline double Determinant (Point &a, Point &b, Point &c)
{
	return a.first * b.second - a.second * b.first + b.first * c.second - b.second * c.first + c.first * a.second - c.second * a.first;
}

inline double Area (Polygon &p)
{
	const int END(p.size());
	double result(0);
	p.push_back(p.front());
	for (int index(0) ; index < END ; ++index)
		result += p[index].first * p[index + 1].second - p[index].second * p[index + 1].first;
	p.pop_back();
	return result / 2;
}

inline bool InPolygon (Polygon &a, Point &b)
{
	const int END(a.size() - 1);
	int index;
	double result(0), area(Area(a));
	for (index = 0 ; index < END ; ++index)
		result += std::abs(Determinant(a[index],a[index + 1],b));
	result /= 2;
	return (result > area - GUARD && result < area + GUARD);
}

inline void Graham (void)
{
	const int END(Points.size());
	int index;
	int sx(0), sy(0), bx(0), by(0);
	for (index = 0 ; index < END ; ++index)
	{
		if (Points[index].first < sx)
			sx = index;
		if (Points[index].first > bx)
			bx = index;
		if (Points[index].second < sy)
			sy = index;
		if (Points[index].second > by)
			by = index;
		if (Points[index] < Points[0])
			std::swap(Points[0],Points[index]);
	}
	Polygon q;
	if (std::find(q.begin(),q.end(),Points[sx]) == q.end())
		q.push_back(Points[sx]);
	if (std::find(q.begin(),q.end(),Points[sy]) == q.end())
		q.push_back(Points[sy]);
	if (std::find(q.begin(),q.end(),Points[bx]) == q.end())
		q.push_back(Points[bx]);
	if (std::find(q.begin(),q.end(),Points[by]) == q.end())
		q.push_back(Points[by]);
	if (q.size() >= 3)
	{
		Polygon tmp;
		for (index = 0 ; index < END ; ++index)
			if (std::find(q.begin(),q.end(),Points[index]) == q.end())
			{
				if (!InPolygon(q,Points[index]))
					tmp.push_back(Points[index]);
			}
			else
				tmp.push_back(Points[index]);
		Points = tmp;
	}
	std::sort(Points.begin() + 1,Points.end(), [ ] (Point a, Point b) -> bool {return Determinant(Points[0],a,b) < 0;});
	Stack[0] = Points[0];
	Stack[1] = Points[1];
	int top(1);
	for (index = 2 ; index < END ; ++index)
	{
		while (top >= 1 && Determinant(Stack[top - 1],Stack[top],Points[index]) > 0)
			--top;
		Stack[++top] = Points[index];
	}
	while (top >= 0)
	{
		Hull.push_back(Stack[top]);
		--top;
	}
}

int main (void)
{
	Read();
	Graham();
	Print();
	return 0;
}