#include <fstream>
#include <algorithm>
#include <vector>

using namespace std;

const char InFile[]="infasuratoare.in";
const char OutFile[]="infasuratoare.out";
const int MaxN=128000;
const double INF=1e250;

ifstream fin(InFile);
ofstream fout(OutFile);

struct s_point
{
	s_point(double _x=0,double _y=0,double _ctg=0):x(_x),y(_y),ctg(_ctg){}
	double x,y,ctg;
};

int N;
s_point p[MaxN];
vector<s_point> v;

struct cmp
{
	inline bool operator() (const s_point &a, const s_point &b)
	{
		return a.ctg<b.ctg;
	}
};

bool convex(s_point P1,s_point P2,s_point P3)
{
	double X1=P1.x, Y1=P1.y; 
	double X2=P2.x, Y2=P2.y;
	double X3=P3.x, Y3=P3.y;
	
	double A=(X2-X1)*(Y3-Y1)-(X3-X1)*(Y2-Y1);
	if(A<0)
	{
		return true;
	}
	return false;
}

void convex_hull(int N, s_point p[], vector<s_point> &v)
{
	double xmin,ymin=INF;
	int O;
	for(register int i=1;i<=N;++i)
	{
		if(ymin>p[i].y)
		{
			ymin=p[i].y;
			xmin=p[i].x;
			O=i;
		}
	}
	
	swap(p[O],p[1]);
	for(register int i=2;i<=N;++i)
	{
		p[i].ctg=(p[i].x-xmin)/(p[i].y-ymin);
	}
	
	sort(p+2,p+N+1,cmp());
	
	int ST[MaxN];
	ST[0]=2;
	ST[1]=1;
	ST[2]=2;
	for(register int i=3;i<=N;++i)
	{
		while(ST[0]>=2 && !convex(p[ST[ST[0]-1]],p[ST[ST[0]]],p[i]))
		{
		
	--ST[0];
		}
		ST[++ST[0]]=i;
	}
	
	v.clear();
	for(register int i=1;i<=ST[0];++i)
	{
		v.push_back(s_point(p[ST[i]].x,p[ST[i]].y));
	}
}

int main()
{
	fin>>N;
	for(register int i=1;i<=N;++i)
	{
		fin>>p[i].x>>p[i].y;
	}
	fin.close();
	
	convex_hull(N,p,v);
	
	fout<<v.size()<<"\n";
	fout.precision(10);
	fout.setf(ios::fixed,ios::floatfield);
	for(vector<s_point>::iterator it=v.begin();it!=v.end();++it)
	{
		fout<<it->x<<" "<<it->y<<"\n";
	}
	fout.close();
	return 0;
}