#include <stdio.h>
#include <algorithm>
using namespace std;
#define max_n 120001
int n,i,h;
typedef struct punct
{
	double x,y;
};
punct p[max_n],v[max_n];
int s[max_n],ok[max_n];
bool cmp(const punct &a,const punct &b)
{
	if(a.y==b.y)
        return a.x<b.x;
    return a.y<b.y;
}
int semn(punct a,punct b,punct c)
{
	double A,B,C;
	A = a.y-b.y;
	B = b.x-a.x;
	C = a.x*b.y - b.x*a.y;
	if(A*c.x+B*c.y+C>0)
        return 1;
    if(A*c.x+B*c.y+C<0)
        return -1;
    return 0;
}
void rezolva()
{
	int k,q;
	sort(v+1,v+n+1,cmp);
	s[1]=1; s[2]=2;
	ok[2]=1;
	k=2;
	i=3;
	q=1;
	while (!ok[1])
	{
		while (ok[i])
		{
			if (i==n) q=-1;
			i+=q;
		}
		while (k>=2 && semn(v[s[k-1]],v[s[k]],v[i])<0)
		{
			ok[s[k--]]=0;
		}
		s[++k]=i;
		ok[i]=1;
	}
	h=k-1;
}

int main ()
{
	freopen("infasuratoare.in","r",stdin);
	freopen("infasuratoare.out","w",stdout);
	scanf("%d",&n);
	for (i=1; i<=n; i++)
		scanf("%lf%lf",&v[i].x,&v[i].y);
	rezolva();
	printf("%d\n",h);
	printf("%lf %lf\n",v[s[h+1]].x,v[s[h+1]].y);
	for (i=2; i<=h; i++)
		printf("%lf %lf\n",v[s[i]].x,v[s[i]].y);

	return 0;
}