#include<stdio.h>
#include<algorithm>
#define nr 120010
#include<math.h>
using namespace std;
int n,k,poz;
struct punct { float x,y;float tg;};
punct v[nr],copie;
float ymin=1000000001.0,xmin=1000000001.0;
int st[nr];

int comp_fa(punct a, punct b)
	{
	if(a.tg==b.tg)
		return a.x<b.x;
	return a.tg<b.tg;		
	}

int deter(int a, int b, int c){
long double x1 = v[a].x;
long double x2 = v[b].x;
long double x3 = v[c].x;
long double y1 = v[a].y;
long double y2 = v[b].y;
long double y3 = v[c].y;long double sol;
sol = (x3 - x2) * (y1 - y2) - (x1 - x2) * (y3 - y2);
if(sol>0) return 1;
else return 0;
}
void infasuratoare()
	{
	copie=v[1];v[1]=v[poz];v[poz]=copie;int i;
	for(i=2;i<=n;i++)
		{
		v[i].x-=xmin;v[i].y-=ymin;
		v[i].tg=v[i].y/v[i].x;
		}
	stable_sort(v,v+n+1,comp_fa);
	st[1]=1;st[2]=2;k=2;	
	for (i = 3; i <= n; i++) {	while (k > 2 && !deter(st[k-1], st[k], i) )	k--;
									k++;st[k]=i;
								}
		
	printf("%d\n%f %f\n", k, v[1].x, v[1].y);
	for (i = 2; i <= k; i++)
		printf("%f %f\n", v[st[i]].x + xmin, v[st[i]].y + ymin);
	}
int main()
	{
	freopen("infasuratoare.in","r",stdin);
	freopen("infasuratoare.out","w",stdout);
	scanf("%d",&n);int i;
	
	for(i=1;i<=n;i++)
			{scanf("%f%f",&v[i].x,&v[i].y);if(ymin>v[i].y)
												{ymin=v[i].y;xmin=v[i].x;poz=i;}
											else
												if(ymin==v[i].y && xmin>v[i].x)
													{ymin=v[i].y;xmin=v[i].x;poz=i;}
			}
	infasuratoare();
	return 0;
	}