#include <stdio.h>
#include <algorithm>
#define NMAX 120005
#define pdd pair <double,double>
#define x first
#define y second
#define eps 0.000001
using namespace std;
int n,r,st[NMAX];
pdd A[NMAX];
bool in[NMAX];
void read()
{
	scanf("%d",&n);
	int i;
	for (i=1; i<=n; i++)
		scanf("%lf%lf",&A[i].x,&A[i].y);
}
inline int semn(pdd a,pdd b,pdd c)
{
	double A=a.y-b.y;
	double B=b.x-a.x;
	double C=a.x*b.y-b.x*a.y;
	double val=(A*c.x+B*c.y+C);
	return (val<eps);
}
void solve()
{
	int i,pas;
	st[++r]=1; st[++r]=2; in[2]=1; i=3; pas=1;
	while (!in[1])
	{
		while (in[i])
		{
			if (i==n)
				pas=-1;
			i+=pas;
		}
		while (r>=2 && semn(A[st[r-1]],A[st[r]],A[i]))
			in[st[r]]=0,r--;
		st[++r]=i; in[i]=1;
	}
	r--;
	printf("%d\n",r);
	for (i=1; i<=r; i++)
		printf("%lf %lf\n",A[st[i]].x,A[st[i]].y);
}
int main()
{
	freopen("infasuratoare.in","r",stdin);
	freopen("infasuratoare.out","w",stdout);
	read();
	sort(A+1,A+n+1);
	solve();
	return 0;
}