#include <fstream>
#include <algorithm>
#include <cmath>
#include <iomanip>
#define NMAX 120005

using namespace std;

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

int i, n, ans = 0;

struct punct
{
    double x, y;
};
punct v[NMAX], stiva[NMAX];

double det(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;
}

bool cmp1(punct a, punct b)
{
    if (a.x == b.x)
        return a.y < b.y;
    return a.x < b.x;
}

bool cmp2(punct a, punct b)
{
    return det(v[1], a, b) < 0;
}

int main()
{
    f >> n;

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

    sort(v + 1, v + n + 1, cmp1);
    sort(v + 2, v + n + 2, cmp2);

    ans = 3;
    stiva[1] = v[1];
    stiva[2] = v[2];
    stiva[3] = v[3];

    for (i = 4; i <= n; ++ i)
    {
        while (ans >= 3 && det(stiva[ans], stiva[ans - 1], v[i]) < 0)
            ans --;
        stiva[++ ans] = v[i];
    }

    g << ans << '\n';

    g << fixed << setprecision(12);
    for (i = ans; i >= 1; -- i)
        g << stiva[i].x << " " << stiva[i].y << '\n';
    return 0;
}