#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;

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

struct Point {
    double x, y;
};

Point v[120100], st[120100];
int n, head;

void Read();
void Write();
void Convex_hull();
double Aria(Point A, Point B, Point C);
int cmp(const Point &A, const Point &B);

int main()
{
    Read();
    Convex_hull();
    Write();
}

void Convex_hull()
{
    int poz = 1;
    for (int i = 2; i <= n; i++)
        if ( v[i].x < v[poz].x )
            poz = i;
    swap(v[1], v[poz]);
    sort(v + 2, v + n + 1, cmp);
    st[1] = v[1];
    st[2] = v[2];
    head = 2;
    for (int i = 3; i <= n; i++)
    {
        while ( Aria(st[head - 1], st[head], v[i]) > 0 )
            head--;
        st[++head] = v[i];
    }
}

int cmp(const Point &A, const Point &B)
{
    return (Aria(v[1], A, B) < 0);
}

double Aria(Point A, Point B, Point C)
{
    return (B.x - A.x) * (C.y - A.y) + (A.y - B.y) * (C.x - A.x);
}

void Write()
{
    fout << head << '\n';
    fout << fixed << setprecision(6);
    for (int i = head; i; i--)
        fout << st[i].x << ' ' << st[i].y << '\n';
    fout.close();
}

void Read()
{
    fin >> n;
    for (int i = 1; i <= n; i++)
        fin >> v[i].x >> v[i].y;
    fin.close();
}