#include <algorithm>
#include <iomanip>
#include <fstream>

using namespace std;

ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

struct punct{
	double x,y;
} v[130000],stack[130000],minim;

double cp(punct a, punct b, punct c)
{
	return (b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x);
}

bool cmp(punct a, punct b)
{
	return cp(v[1],a,b);
}

int n,i,j,poz,vf;

int main()
{
	fin>>n;
	i=1;
	fin>>v[1].x>>v[1].y;
	minim.x=v[1].x;
	minim.y=v[1].y;
	poz=1;	
	for (i=2; i<=n; i++)
	{
		fin>>v[i].x>>v[i].y;
		if (v[i].x<minim.x||(v[i].x==minim.x&&v[i].y<minim.y))
			minim.x=v[i].x,minim.y=v[i].y,poz=i;
	}
	swap(v[1],v[poz]);
	sort(v+2,v+n+1,cmp);
	stack[1]=v[1];
	stack[2]=v[2];
	vf=2;
	for (i=3; i<=n; i++)
		{
			while (vf>=2&&cp(stack[vf-1],stack[vf],v[i])>0)
				vf--;
			stack[++vf]=v[i];
		}
	fout<<vf<<'\n';
	for (i=1; i<=n; i++)
		fout<<fixed<<setprecision(9)<<v[i].x<<' '<<v[i].y<<'\n';	
}