#include<fstream.h>
#include<math.h>
#include<algorithm>
#include<iomanip.h>
using namespace std;
struct punct{double x,y,d;}p[120000],p0,s[120000];
int i,n,k,j,ps;
double pr;

inline void sch(punct &q,punct &w)
{
	punct aux;
	aux=q;q=w;w=aux;
}

void cauta_primul()
{
	int i,im;
	im=0;
	for (i=1;i<n;i++)
		if (p[i].y<p[im].y) im=i;
			else if (p[i].y==p[im].y&&p[i].x<p[im].x) im=i;
	sch(p[0],p[im]);
}

inline double status(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;
}

double dist(punct A, punct B)
{
	double u,v;
	u=A.x-B.x;
	v=A.y-B.y;
	return sqrt(u*u+v*v);
}

int cmp(punct x,punct y)
{
	double pr;
	pr=status(p0,x,y);
    if (pr<0||pr==0&&x.d<y.d) return 0;
	return 1;
}

int main()
{
	ifstream f("grader_test6.in");
	ofstream g("infasuratoare.out");
	f>>n;
	for (i=0;i<n;++i) f>>p[i].x>>p[i].y;
	cauta_primul();p0=p[0];
	for (i=2;i<=n;i++)p[i].d=dist(p0,p[i]);
	/*do
	{
		k=0;
		for (i=2;i<n;++i)
		{
			pr=status(p0,p[i],p[i+1]);
			if (pr<0||pr==0&&p[i].d<p[i+1].d)
			{
				sch(p[i],p[i+1]);
				k=1;
			}
		}
	}while (k==1);*/
	sort(p+1,p+n,cmp);
	//qsort(p,n,sizeof(punct),cmp);

	i=1;
	s[0]=p[0];
	s[1]=p[1];
	for (j=2;j<n;++j)
		if (status(p0,p[j-1],p[j])>0){++i;s[i]=p[j];}
	
	
	for (j=0;j<=i;++j) p[j]=s[j];
	n=i+1;
	ps=2;
	for (i=3;i<n;++i)
	{
		do
		{ 
			pr=status(s[ps-1],s[ps],p[i]);
			if (pr<0) --ps;
		}while(pr<0);
		s[++ps]=p[i];
	}
	g<<ps+1<<"\n";
	for (i=0;i<=ps;++i)
		{g<<setprecision(12)<<s[i].x;
	     g<<" "<<setprecision(12)<<s[i].y<<"\n";}
	f.close();
	g.close();
	return 0;
}