#include <fstream>
#include <algorithm>
#include <vector>
#include <iomanip>
using namespace std;
const int NMAX = 120004;

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

int stiva[NMAX];

double ccw(pct a, pct b, pct c)
{
    return (b.y - a.y) * (b.x - c.x) - (b.y - c.y) * (b.x - a.x);
}

bool cmp(pct a, pct b)
{
    return ccw(v[1], a, b) < 0;
}
int main()
{
    ifstream cin("infasuratoare.in");
    ofstream cout("infasuratoare.out");
    int n, i;
    cin >> n;
    int poz = 1;
    for (i = 1; i <= n; i++)
    {
        cin >> v[i].x >> v[i].y;
        if (v[i].x < v[poz].x)
        {
            poz = i;
        }
    }
    swap(v[1], v[poz]);
    sort(v + 2, v + n + 1, cmp);
    stiva[1] = 1;
    stiva[2] = 2;
    int top = 2;
    for (i = 3; i <= n; i++)
    {
        while (top > 1 and ccw(v[stiva[top - 1]], v[stiva[top]], v[i]) > 0)
        {
            top--;
        }
        stiva[++top] = i;
    }
    cout << top << "\n";
    for (i = top; i >= 1; i--)
        cout << fixed << setprecision(12) << v[stiva[i]].x << " " << v[stiva[i]].y << "\n";
}