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

using namespace std;

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

struct point
{
    double x, y;

    point()
    {
        x = 0;
        y = 0;
    }

    point(double X, double Y)
    {
        x = X;
        y = Y;
    }

    bool operator < (const point &that) const
    {
        if (x < that.x)
            return true;

        if (x == that.x && y < that.y)
            return true;

        return false;
    }

    bool operator > (const point &that) const
    {
        return !(*this < that);
    }
};

int n;

int st[120001];

point v[120001];

double 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;

    int first = 1;
    for (int i=2; i<=n; i++)
        if (v[i] < v[first])
            first = i;

    swap(v[1], v[first]);

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

    int 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;
    }

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

    return 0;
}