#include <cstdio>
#include <algorithm>
#define NMAX 120023
using namespace std;
FILE *fin, *fout;
int n, p, sum, stiva[NMAX];
bool f;
struct punct
{
	double x;
	double y;
	double f1;
	double f2;
} v[NMAX];
bool comp(punct a, punct b)
{
	return (a.f1 * b.f2 < b.f1 * a.f2);
}
double calcarie(double x1,double y1,double x2,double y2,double x3,double y3)
{
       double arie=double((double)x1*(y2-y3)+(double)x2*(y3-y1)+(double)x3*(y1-y2));
       arie=(double)arie/2;
       return arie;
}
int main()
{
	fin = freopen("infasuratoare.in", "r", stdin);
	fout = freopen("infasuratoare.out", "w", stdout);
	scanf("%d", &n);
	for(int i = 0; i< n; i++)
	{
		scanf("%lf %lf", &v[i].x, &v[i].y);
		if(i == 0) continue;
		if(v[i].x < v[p].x) p = i;
		else if(v[i].x == v[p].x)
		{
			if(v[i].y < v[p].y) p = i;
		}
	}
	swap(v[p], v[0]);
	for(int i = 1; i< n; i++)
	{
		v[i].f1 = v[i].y - v[0].y;
		v[i].f2 = v[i].x - v[0].x;
	}
	sort(v+1, v+n, comp);
	stiva[1] = 1;
	p = 2;
	for(int i = 2; i< n; i++)
	{
		while(calcarie(v[stiva[p-2]].x,v[stiva[p-2]].y, v[stiva[p-1]].x, v[stiva[p-1]].y, v[i].x, v[i].y) < 0) p--;
		stiva[p] = i;
		p++;
	}
	printf("%d\n", p);
	for(int i = 0; i< p; i++) printf("%lf %lf\n", v[stiva[i]].x, v[stiva[i]].y);
	fclose(fin);
	fclose(fout);
	return 0;
}