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

using namespace std;
const int Nmax = 120001;

struct punct
{
    double x, y;
};

int N, nrp;
punct P[Nmax], St[Nmax];

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

double det(const punct &A, const punct &B, const punct &C)
{
    return (A.x - B.x) * (A.y - C.y) - (A.y - B.y) * (A.x - C.x) ;
}

bool compd(const punct &A, const punct &B)
{
    return det(P[1], A, B) < 0;
}

bool compx(const punct &A, const punct &B)
{
    if(A.x == B.x) return A.y < B.y;
    return A.x < B.x;
}

void citire()
{
    f >> N;
    int pmin = 1; //pozitia celui mai mic x
    for(int i = 1; i <= N; i++)
    {
        f >> P[i].x >> P[i].y;
        if(compx(P[i], P[pmin]))
            pmin = i;
    }
    swap(P[1], P[pmin]);
}

void afisare()
{
    g << nrp << '\n';
    g << fixed << setprecision(6);
    for(int i = nrp; i >= 1; i--)
        g << St[i].x << ' ' << St[i].y << '\n';
}

void Graham()
{
    sort(P + 2, P + N + 1, compd);
    St[1] = P[1];
    St[2] = P[2];
    nrp = 2;
    for(int i = 3; i <= N; i++)
    {
        while(nrp >= 2 && det(St[nrp - 1], St[nrp], P[i]) > 0)
            nrp--;
        St[++nrp] = P[i];
    }
}

int main()
{
    citire();
    Graham();
    afisare();
    return 0;
}