#include<fstream>
#include<iomanip>
#include<algorithm>
#include<cmath>
#define NMAX 120010
#define EPS 0.00000000001

using namespace std;

ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");

struct punct
{
	double x, y;
	int o;
}a[NMAX];
int n, st1[NMAX], st2[NMAX];

void Citeste()
{
	int i;
	f>>n;
	for (i=1; i<=n; ++i) f>>a[i].x>>a[i].y;
}

inline bool cmp(punct A, punct B)
{
	if (fabs(A.x-B.x)<EPS)
		if (A.y-B.y<EPS) return 1;
		else return 0;
	else if (A.x-B.x<EPS) return 1;
			else return 0;
}

double plan(punct A, punct B, punct C)
{
	return A.x*B.y+B.x*C.y+C.x*A.y-B.y*C.x-C.y*A.x-A.y*B.x;
}

void Solve()
{
	int i, m1=2, m2=2;
	double P;
	
	st1[1]=1; st1[2]=2; m1=2;
	for (i=3; i<=n; ++i)
	{
		P=plan(a[st1[m1-1]], a[st1[m1]], a[i]);
		if (P<EPS) st1[++m1]=i;
		else 
		{
			while (P>EPS && m1>2)
			{
				--m1;
				P=plan(a[st1[m1-1]], a[st1[m1]], a[i]);
			}
			if (P<EPS) st1[++m1]=i;
		}
	}
	
	for (i=2; i<=m1; ++i) a[st1[i]].o=1;
	
	st2[1]=n; st2[2]=n-1; m2=2;
	for (i=n-2; i>0; --i)
		if (!a[i].o)
		{
			P=plan(a[st2[m2-1]], a[st2[m2]], a[i]);
			if (P<EPS) st2[++m2]=i;
			else 
			{
				while (P>EPS && m2>2)
				{
					--m2;
					P=plan(a[st2[m2-1]], a[st2[m2]], a[i]);
				}
				if (P<EPS) st2[++m2]=i;
			}
		}
	g<<m1+m2-2<<"\n";
	for (i=m1; i>0; --i) g<<fixed<<a[st1[i]].x<<" "<<a[st1[i]].y<<"\n";
	for (i=m2-1; i>1; --i) g<<fixed<<a[st2[i]].x<<" "<<a[st2[i]].y<<"\n";
}

int main()
{
	Citeste();
	sort(a+1, a+n+1, cmp);
	Solve();
	f.close();
	g.close();
	return 0;
}