#include <bits/stdc++.h>
using namespace std;
double INF = 1000000004;

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

int n;
struct point
{
    double x, y;
};
point p0;
vector<point> points;
vector<point> rez;

int orientation(point a, point b, point c)
{
    double v = (b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x);
    if (v < 0)
    {
        return -1;
    }
    if (v > 0)
    {
        return 1;
    }
    return 0;
}
bool ccw(point a, point b, point c, bool include_collinear)
{
    int o = orientation(a, b, c);
    return o > 0 || (include_collinear && o == 0);
}

bool collinear(point a, point b, point c)
{
    return orientation(a, b, c) == 0;
}

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

bool cmp(point a, point b)
{
    if (orientation(p0, a, b) == 0)
    {
        return dist(p0, a) < dist(p0, b);
    }
    return orientation(p0, a, b) > 0;
}

void convex_hull(bool include_collinear = false)
{
    p0 = {INF, INF};
    for (auto point : points)
    {
        if (point.y < p0.y)
        {
            p0 = point;
        }
        else if (point.y == p0.y && point.x < p0.x)
        {
            p0 = point;
        }
    }
    sort(points.begin(), points.end(), cmp);
    if (include_collinear)
    {
        int i = (int)points.size() - 1;
        while (i >= 0 && collinear(p0, points[i], points.back()))
        {
            i--;
        }
        reverse(points.begin() + i + 1, points.end());
    }
    for (int i = 0; i < (int)points.size(); i++)
    {
        while (rez.size() >= 2 && !ccw(rez[rez.size() - 2], rez.back(), points[i], include_collinear))
        {
            rez.pop_back();
        }
        rez.push_back(points[i]);
    }
}

int main()
{
    fin >> n;
    for (int i = 1; i <= n; i++)
    {
        double x, y;
        fin >> x >> y;
        points.push_back({x, y});
    }
    convex_hull();
    fout << rez.size() << '\n';
    for (auto point : rez)
    {
        fout << fixed << setprecision(6) << point.x << ' ' << point.y << '\n';
    }
    return 0;
}