#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>

using namespace std;

struct punct
{
    double x, y;
    punct(double x = 0, double y = 0) : x(x), y(y) { }
    bool operator()(punct a, punct b)
    {
        if (a.x != b.x)
			return a.x < b.x;
		return a.y < b.y;
    }
};
int n;
vector<punct> poly;
vector<punct> s1, s2;

void citire()
{
    double x, y;
    scanf("%d\n", &n);
    for (int i = 1; i <= n; i++) {
		scanf("%lf %lf\n", &x, &y);
		poly.push_back(punct(x, y));
    }
}

double determinant(punct a, punct b, punct c)
{
    return a.x*b.y + b.x*c.y + c.x*a.y - c.x*b.y - b.x*a.y - a.x*c.y;
}

void add(vector<punct> &s, punct p)
{
    while (s.size() >= 2 && determinant(s[s.size()-2], s[s.size()-1], p) < 0)
		s.pop_back();
    s.push_back(p);
}

void solve()
{
	sort(poly.begin(), poly.end(), punct());
	s1.push_back(poly[0]);
	for (int i = 1, t = poly.size(); i < t; i++)
        add(s1, poly[i]);
	s2.push_back(poly.back());
    for (int i = poly.size()-2; i >= 0; --i)
		add(s2, poly[i]);
    s1.pop_back();
    s2.pop_back();
    for (int i = 0, t = s2.size(); i < t; i++)
        s1.push_back(s2[i]);
	printf("%d\n", s1.size());
    for (int i = 0, t = s1.size(); i < t; i++)
		printf("%lf %lf\n", s1[i].x, s1[i].y);
}

int main()
{
    freopen("infasuratoare.in", "r", stdin);
    freopen("infasuratoare.out", "w", stdout);

    citire();
    solve();

    return 0;
}