#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];
long 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()
{
	long 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 prod(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 compara (const void * a, const void * b)
{
	//return ( *(int*)a - *(int*)b );

    punct u,v;
	u=*((punct*)a);
	v=*((punct*)b);
	double pr;
	pr=prod(p0,v,u);
	if(u.x==v.x &&u.y==v.y)return 0;
    if (pr<0||pr==0&&u.d>v.d) return -1;
	return 1;
}

int main()
{long i;
	ifstream f("infasuratoare.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=1;i<n;i++) p[i].d=dist(p0,p[i]);
	i=n-1;
	punct *t;
	t=p+1;	
	qsort(t,i,sizeof(punct),compara);
	i=1;
	s[0]=p[0];
	s[1]=p[1];
	
	for (j=2;j<n;++j)
		if (prod(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=prod(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;
}