#include <fstream>
#include <cstdio>
#include <algorithm>

using namespace std;

ifstream f("infasuratoare.in");
FILE *g=fopen("infasuratoare.out","w");

struct punct
{
    double x,y;
} p[120001];

int s[120001],r,k,infinit,v[120001],vf,n;
char nr[31];

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

void reper()
{
    r=1;
    for(int i=2;i<=n;i++)
	  if(p[i].x<p[r].x||p[i].x==p[r].x&&p[i].y<p[r].y) r=i;
}

int mai_mic(int i,int j)
{
    double a=(p[i].x-p[r].x)*(p[j].x-p[r].x);
    double b=(p[i].y-p[r].y)*(p[j].x-p[r].x)-(p[i].x-p[r].x)*(p[j].y-p[r].y);
    if(a<0&&b>0||a>0&&b<0) return 1;
    return 0;
}

void ordonare()
{
    k=0;
    int i;
    for(i=1;i<=n;i++)
        if(i!=r)
		  if(p[i].x==p[r].x)
			  if(!infinit||p[infinit].y<p[i].y) infinit=i;
				  else;
			  else k++, v[k]=i;
    sort(v+1,v+k+1,mai_mic);
}

int elim(int i)
{
    double a=p[v[i]].x-p[s[vf]].x;
    double b=(p[s[vf-1]].y-p[v[i]].y)*a-(p[v[i]].y-p[s[vf]].y)*(p[s[vf-1]].x-p[v[i]].x);
    if(b<=0) return 1;
    return 0;
}

void stiva()
{
    s[1]=r;
    s[2]=v[1];
    vf=2;
    for(int i=2;i<=k;i++)
    {
        while(elim(i)&&vf>2) vf--;
	    vf++;
		s[vf]=v[i];
    }
}

void afis()
{
    if(infinit)  fprintf(g,"%d\n",vf+1);
        else fprintf(g,"%d\n",vf);
    for(int i=1;i<=vf;i++) fprintf(g,"%.6lf %.6lf\n",p[s[i]].x,p[s[i]].y);
    if(infinit)fprintf(g,"%.6lf %.6lf\n",p[infinit].x,p[infinit].y);
}

int main()
{
    citire(); reper(); ordonare(); stiva(); afis();
    fclose(g);
    return 0;
}