#include<fstream.h>
#include<iomanip.h>

using namespace std;

double x[125000],y[125000],val1,val2;
long a[125000],sol[125000],cont,mi;

void qs(long i, long j)
{
	long s=i,d=j,aux,piv=((i+j)>>1);
	while(s<=d)
	{
		while((y[a[s]]-val2)*(x[a[piv]]-val1)<(y[a[piv]]-val2)*(x[a[s]]-val1))s++;
		while((y[a[d]]-val2)*(x[a[piv]]-val1)>(y[a[piv]]-val2)*(x[a[d]]-val1))d--;
		if(s<d)
		{
			aux=a[s];
			a[s]=a[d];
			a[d]=aux;
			d--;
			s++;
		}
	}
	if(i<d)qs(i,d);
	if(s<j)qs(s,j);
}
	
int det(long i1, long i2, long i3)
{
	if(x[i1]*y[i2]+x[i2]*y[i3]+x[i3]*y[i1]>y[i1]*x[i2]+y[i2]*x[i3]+y[i3]*x[i1]) return 1;
	else return 0;
}
	
int main()
{ 
	long n,i,j,gasit,k,temp1,temp2,aux;
	ifstream f("infasuratoare.in");
	ofstream g("infasuratoare.out");
	f>>n>>x[1]>>y[1];
	mi=1;
	for(i=2;i<=n;i++)
	{
		f>>x[i]>>y[i];
		if(x[i]<x[mi])mi=i;
		else if(x[i]==x[mi])if(y[i]<y[mi])mi=i;
	}
	val1=x[mi];
	val2=y[mi];
	for(i=mi;i<n;i++){x[i]=x[i+1];y[i]=y[i+1];}
	x[n]=val1;
	y[n]=val2;
	for(i=1;i<=n;i++)a[i]=i;
	for(i=1;i<n-1;i++)
		for(j=i+1;j<n;j++)
			if((y[a[j]]-val2)*(x[a[i]]-val1)<(y[a[i]]-val2)*(x[a[j]]-val1))
			{
				aux=a[i];
				a[i]=a[j];
				a[j]=aux;
			}
	for(i=1;i<n;i++)cout<<x[a[i]]<<' '<<y[a[i]]<<endl;
	sol[1]=a[n];
	sol[2]=a[1];
	i=2;j=2;
	while(j<n)
	{
		if(det(sol[i-1],sol[i],a[j]))sol[++i]=a[j++];			
		else
		{
			while(!det(sol[i-1],sol[i],a[j]))i--;
			sol[++i]=a[j++];
		}
	}
	g<<i<<'\n';
	for(j=1;j<=i;j++)g<<fixed<<setprecision(6)<<x[sol[j]]<<' '<<y[sol[j]]<<'\n';
	return 0;
}