#include<fstream>
#include<iostream>
#include<algorithm>
using namespace std;
#define nn 120005
struct puncte{
	double x,y;	
};
puncte v[nn];
int z[nn],n,m;
double directie(int a,int b,int c)
{
	return ((v[b].x-v[a].x)*(v[c].y-v[a].y)-(v[b].y-v[a].y)*(v[c].x-v[a].x));
}
double functie(puncte a,puncte b)
{
	return (double)(a.x - v[1].x) * (b.y - v[1].y) > (double)(b.x - v[1].x) * (a.y - v[1].y);
}

int dir(puncte A,puncte B,puncte C)
{
    double det=A.x*B.y+B.x*C.y+C.x*A.y-C.x*B.y-B.x*A.y-A.x*C.y;
    if(det==0)
      return 0;
    if(det<0)
      return -1;
    return 1;
}
int polare(puncte A,puncte B)
{
    if(dir(v[1],A,B)>0)
      return 1;
    if(dir(v[1],A,B)<0)
      return 0;
    return(v[1].x-A.x)*(v[1].x-A.x)+(v[1].y-A.y)*(v[1].y-A.y) <
          (v[1].x-B.x)*(v[1].x-B.x)+(v[1].y-B.y)*(v[1].y-B.y);
}

void infasor(int pmin)
{
	sort(v+2,v+n,polare);
	z[++m]=pmin;
	int gata=0;
	for(int i=2;i<n;++i)
    {
		while(directie(z[m-1],z[m],i)<=0 && m>1)
        --m;
		z[++m]=i;
    }
}
int main()
{
	ifstream fin("infasuratoare.in");
	fin>>n;
	for(int i=1;i<=n;++i)
		fin>>v[i].x>>v[i].y;
	int pmin=1;
	for(int i=2;i<=n;++i)
		if(v[i].y<v[pmin].y)
			pmin=i;
		else if(v[i].x==v[pmin].x)
				if(v[i].x<v[pmin].x)
					pmin=i;
	puncte aux=v[pmin];
	v[pmin]=v[1];
	v[1]=aux;
	infasor(pmin);
	FILE *f=fopen("infasuratoare.out","w");
	//ofstream fout("infasuratoare.out");
	fprintf(f,"%d\n",m);
	//fout<<m-1<<"\n";
	for(int i=1;i<=m;++i)
		//fout<<v[z[i]].x<<" "<<v[z[i]].y<<"\n";
		fprintf(f,"%f %f\n",v[z[i]].x,v[z[i]].y);
	return 0;
}