#include<cstdio>
#include<math.h>
#include<algorithm>
#define PI 3.14159265
using namespace std;
int n,poz,varf;

const double oo=1000000002;
const int maxn=120002;
double minix=oo,miniy;
struct muchie{
	double x,y;
};	
muchie v[maxn],check[maxn];

double panta(muchie A , muchie B , muchie C){
	return (B.x-A.x)*(C.y-A.y)-(C.x-A.x)*(B.y-A.y);
}

int compare( const muchie D, const muchie E){
	return panta(v[1],D,E)<0 ;
} 
 

int main(){
	freopen("infasuratoare.in","r",stdin);
	freopen("infasuratoare.out","w",stdout);
	scanf("%d",&n);
	for (int i=1;i<=n;++i){
		scanf("%lf %lf",&v[i].x,&v[i].y);
		if(v[i].x<minix){
			minix=v[i].x;
			miniy=v[i].y;
			poz=i;
		}
		else
			if(v[i].x==minix)
				if(v[i].y<miniy){
					miniy=v[i].y;
					poz=i;
				}
	}
	swap(v[1],v[poz]);
	sort(v+2,v+n+1,compare );
	varf=2;
	check[1]=v[1];
	check[2]=v[2];
	for(int i=3;i<=n;++i){
		while(varf>=2 && panta(check[varf-1],check[varf],v[i])>0){
			--varf;
		}
		varf++;
		check[varf]=v[i];
	}
	printf("%d\n",varf);
	for(int i=varf;i>=1;--i)
		printf("%lf %lf\n", check[i].x,check[i].y);
	return 0;
}