#include <fstream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <iomanip>
#include <stack>
using namespace std;

ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

const double oo = 0x3f3f3f3f;
const int NMAX = 120003;
struct point
{
	double x, y;
};

vector <point> v;


double determ(point a, point b, point c)
{
	return (b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x);
}

inline bool cmp(point a, point b)
{
	return determ(a, b, v[0]) < 0;
}

int n, start;

point a, mini;

point st[NMAX];

int main()
{
	mini.x = oo;
	mini.y = oo;
	fin >> n;
	for (int i = 0; i < n; ++i)
	{
		fin >> a.x >> a.y;
		v.push_back(a);
		if ((a.x < mini.x) ||(a.x == mini.x && a.y < mini.y))
		{
			mini = a;
			start = i;
		}
	}
	
	swap(v[start], v[0]);

	sort(v.begin(), v.end(), cmp);
	
	st[0] = v[0];
	st[1] = v[1];
	int vf = 1;

	for (int i = 2; i < n; ++i)
	{
		while (vf && determ(st[vf - 1], st[vf], v[i]) > 0)
			--vf;
		st[++vf] = v[i];
	}
	fout << vf + 1 << "\n";
	fout << fixed << setprecision(6);
	while (vf >= 0)
	{
		fout << st[vf].x << " " << st[vf].y << "\n";
		--vf;
	}
	return 0;
}