#include<fstream.h>
#include<math.h>
#include<algorithm>
#include<iomanip.h>
using namespace std;

struct punct{
	double x,y,d;
};

punct p[120000],p0,s[120000];

 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;
	}

 int compara (const void * a, const void * b)
{
  //return ( *(int*)a - *(int*)b );



 punct A,B;

	A=*(punct*)a;
	B=*(punct*)b;
	double pr=prod(p[1],B,A);
	if(pr<0)return -1;
	if(pr==0&&A.d>B.d)return -1;
	if(A.x==B.x&&A.y==B.y)return 0;
	return 1;
	}
            


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=1;
	for (i=2;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[1],p[im]);
}


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 main()
{long i,m;
	ifstream f("infasuratoare.in");
	ofstream g("infasuratoare.out");
	f>>n;
	for (i=1;i<=n;++i) f>>p[i].x>>p[i].y;
	cauta_primul();
	p0=p[1];
	for (i=2;i<=n;i++) p[i].d=dist(p0,p[i]);
	                    
	qsort(p+2,n-1,sizeof(punct),compara);
	
	i=1;
	s[1]=p[1];
	s[2]=p[2];
	m=2;
	for (j=3;j<=n;++j)
		if (prod(p0,p[j-1],p[j])>0){++m;s[m]=p[j];}
	
	
	for (j=1;j<=m;++j) p[j]=s[j];
	n=m;
	ps=3;
	for (i=4;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<<"\n";
	for (i=1;i<=ps;++i)
		{g<<fixed<<s[i].x<<' '<<s[i].y<<"\n";
			
		}
	f.close();
	g.close();
	return 0;
}