#include <fstream>
#include <iostream>
#include <algorithm>
#include<iomanip>

using namespace std;

ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");

struct point
{
    double x, y;
};

int n, m;

int st[100005];

point v[100005];

long long cross_product(const point& a, const point& b, const point& c)
{
    return (b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x);
}

bool cmp(const point& a, const point& b)
{
    return cross_product(v[1], a, b) < 0;
}

int main()
{
    f >> n;

    for (int i = 1; i <= n; i++)
        f >> v[i].x >> v[i].y;

    for (int i = 2; i <= n; i++)
        if ((v[i].x < v[1].x) || (v[1].x == v[i].x && v[i].y < v[1].y))
            swap(v[i], v[1]);

    sort(v + 2, v + n + 1, cmp);

    m = 2;
    st[1] = 1;
    st[2] = 2;

    for (int i = 3; i <= n; i++)
    {
        while (m > 2 && cross_product(v[st[m - 1]], v[st[m]], v[i]) >= 0)
            m--;

        m++;
        st[m] = i;
    }

    while (cross_product(v[1], v[st[m]], v[st[m-1]]) == 0)
        m--;

    int start = m;
    for (int i = 1; i <= m; i++)
        if ((v[st[i]].y < v[st[start]].y) ||
            (v[st[i]].y == v[st[start]].y && v[st[i]].x < v[st[start]].x))
            start = i;


    g << m << "\n";
    for (int i = start; i >= 1; i--)
        g << v[st[i]].x << " " << v[st[i]].y << "\n";
    for (int i = m; i > start; i--)
        g << fixed<<setprecision(6)<<v[st[i]].x << " " << v[st[i]].y << "\n";

    return 0;
}