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

using namespace std;

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

const int Nmax = 120005;

int n, varf;

struct punct
{
    double x;
    double y;
}v[Nmax];

vector<punct> Q(Nmax);

int intoarcere (punct P0, punct P1, punct P2)
{
    return (P1.x - P0.x) * (P2.y - P0.y) - (P2.x - P0.x) * (P1.y - P0.y);
}

bool cmp(punct A,punct B)
{
    if (A.y == B.y)
        return A.x < B.x;

    return A.y < B.y;
}


int main()
{
    in >> n;

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

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

    Q[++varf] = v[1];
    Q[++varf] = v[2];

    for (int i = 3; i <= n; i++)
    {
        int val = intoarcere (Q[varf - 1], Q[varf], v[i]);

        if (val == 0)
        {
            varf--;
            Q[++varf] = v[i];
        }

        else

         if (val > 0)
        Q[++varf] = v[i];

        else

        {
            while (val <= 0 && varf > 1)
            {
                varf--;
                val = intoarcere(Q[varf - 1], Q[varf], v[i]);
            }

            Q[++varf] = v[i];
        }
    }

    Q[++varf] = v[n - 1];

    for (int i = n - 2; i >= 2; i--)
    {
        int val = intoarcere (Q[varf - 1], Q[varf], v[i]);

        if (val == 0)
        {
            varf--;
            Q[++varf] = v[i];
        }

        else

         if (val > 0)
        Q[++varf] = v[i];

        else

        {
            while (val <= 0 && varf > 1)
            {
                varf--;
                val = intoarcere(Q[varf - 1], Q[varf], v[i]);
            }

            Q[++varf] = v[i];
        }
    }

    out << varf << '\n';
    for (int i = 1; i <= varf; i++)
        out << fixed << setprecision(12) << Q[i].x << ' ' << Q[i].y << '\n';
}