#include <stdio.h>
#include <algorithm>
#define N 120001
using namespace std;
typedef struct {float x,y;} PUNCT;
PUNCT X[N];
PUNCT S[N];
int n,i,s;

FILE *f,*g;

bool operator < (const PUNCT &a, const PUNCT &b)
{
	if (a.y<b.y)
		return 1;
	else if (a.y==b.y)
		if (a.x<b.x)
			return 1;
	return 0;
}

int stanga(PUNCT &a, PUNCT &b, PUNCT &c)
{
	float st;
	st=a.x*b.y+b.x*c.y+c.x*a.y-b.y*c.x-a.y*b.x-c.y*a.x;
	if (st>0)
		return 1;
	else return 0;
}

int main()
{
	f=fopen("infasuratoare.in","r");
	g=fopen("infasuratoare.out","w");
	fscanf(f,"%d",&n);
	for (i=1;i<=n;++i)
		fscanf(f,"%f %f",&X[i].x,&X[i].y);
	sort(X+1,X+n+1);
	s=2;
	S[1]=X[1];
	S[2]=X[2];
	i=3;
	while (i<=n)
	{
		if (stanga(S[s-1],S[s],X[i]))
		{
			S[++s]=X[i];
			++i;
		}
		else
		{
			s--;
			if (s<2)
			{
				S[++s]=X[i];
				++i;
			}
		}
	}
	i=n-1;
	while (i>1)
	{
		if (stanga(S[s-1],S[s],X[i]))
		{
			S[++s]=X[i];
			i--;
		}
		else if (X[i].x!=S[s].x || X[i].y!=S[s].y)
		{
				if (X[i].x!=S[s-1].x || X[i].x!=S[s-1].y)
					s--;
				else i--;
		}
		else i--;
	}
	fprintf(g,"%d\n",s);
	for (i=1;i<=s;++i)
		fprintf(g,"%f %f\n",S[i].x,S[i].y);
	fclose(f);
	fclose(g);
	return 0;
}