#include<fstream.h>
#include<iomanip.h>
#include<math.h>
double x[100100],y[100100],p[100100],xx[100100];
long a[100100],sol[100100],ssol[100100],mi;
long ls(long k)
{
 return (k<<1);
 }
long rs(long k)
{
 return ((k<<1)+1);
 }
long f(long k)
{
 return (k>>1);
 }
double dist(long i, long j)
{
	double d=(x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]);
	return d;
}
void ex(long x, long y)
{
 long aux;
 aux=a[x];
 a[x]=a[y];
 a[y]=aux;
 }
void sift(long n, long k)
{
 long son;
 do
  {
   son=0;
   if(ls(k)<=n)
    {
     son=ls(k);
     if(rs(k)<=n&&(p[a[rs(k)]]>p[a[son]]||p[a[rs(k)]]==p[a[son]]&&dist(a[rs(k)],mi)>dist(a[son],mi)))son=rs(k);
     if(p[a[son]]<p[a[k]]||p[a[son]]==p[a[k]]&&dist(a[son],mi)<dist(a[k],mi))son=0;
     }
   if(son)
    {
     ex(k,son);
     k=son;
     }
    }
   while(son);
 }
void bh(long n)
{
 long i;
 for(i=(n>>1);i;i--)sift(n,i);
 }
void batman(long n)
{
	long i;
	bh(n);
	for(i=n;i>1;i--)
	{
		ex(1,i);
		sift(i-1,1);
	}
}
int det(long q, long w, long e)
{
	if(x[q]*y[w]+x[w]*y[e]+x[e]*y[q]>x[w]*y[q]+x[e]*y[w]+x[q]*y[e])return 2;
	else 
		if(x[q]*y[w]+x[w]*y[e]+x[e]*y[q]==x[w]*y[q]+x[e]*y[w]+x[q]*y[e])return 1;
		else return 0;
}
int main()
{ 
	long max,k,n,j,i,t,b[100100],i1,i2;
	double numa,numi,d,dmax,s,smax,l;
	ifstream f("infasuratoare.in");
	ofstream g("infasuratoare.out");
	f>>n>>x[1]>>y[1];
	mi=1;
	t=0;
	for(i=2;i<=n;i++)
	{
		f>>x[i]>>y[i];
		if(x[i]<x[mi]||x[i]==x[mi]&&y[i]<y[mi])mi=i;
	}
	k=0;
		for(i=1;i<=n;i++)
			if(x[mi]==x[i])b[++k]=i;
			else 
				{
					p[i]=(y[i]-y[mi])/(x[i]-x[mi]);
					a[++t]=i;
				}
		max=b[1];
		for(i=2;i<=k;i++)
			if(y[b[i]]>y[max])max=b[i];
		batman(t);
		ssol[1]=mi;
		ssol[2]=a[1];
		i=2;j=2;
		while(j<=t)
		{
			while(!det(ssol[i-1],ssol[i],a[j]))
				i--;
			ssol[++i]=a[j++];
		}
		if(k>1&&max!=mi)
			ssol[++i]=max;
		while(!det(ssol[i-2],ssol[i-1],ssol[i]))
		{
			ssol[i-1]=ssol[i];
			i--;
		}
		sol[1]=ssol[1];
		sol[2]=ssol[2];
		k=2;
		for(j=3;j<=i;j++)
		{
			if(det(sol[k-1],sol[k],ssol[j])==1)sol[k]=ssol[j];
			else sol[++k]=ssol[j];
		}
		i=k;	
	g<<i<<'\n';
	for(j=1;j<=i;j++)g<<fixed<<setprecision(6)<<x[sol[j]]<<' '<<y[sol[j]]<<'\n';
	return 0;
}