#include <iostream>
#include <stdio.h>
#include <stack>
#define INF 0x3f3f3f
#define NMAX 120001
using namespace std;

int n;
struct puncte{
    double x,y,pante;
};
puncte a[NMAX];
double pxmin,pymin;
int pozmin;
stack < int > S;
double calcularepanta(int xx)
{
    if (a[0].x==a[xx].x)
        return INF;
    return ((a[xx].y-a[0].y)/(a[xx].x-a[0].x));


}



void citire()
{

    freopen("infasuratoare.in","r",stdin);

    scanf("%d",&n);
    scanf("%lg%lg",&a[1].x,&a[1].y);
    pxmin=a[1].x;
    pymin=a[1].y;pozmin=1;
    for (int i=2;i<=n;++i)
    {
        scanf("%lg%lg",&a[i].x,&a[i].y);
        if (a[i].x<pxmin)
            pxmin=a[i].x,pymin=a[i].y,pozmin=i;
        else if (a[i].x==pxmin && a[i].y<pymin)
            pxmin=a[i].x,pymin=a[i].y,pozmin=i;
    }
    a[0].x=pxmin;
    a[0].y=pymin;
    a[pozmin].x=a[n].x;
    a[pozmin].y=a[n].y;
    --n;
    for (int i=1;i<=n;++i)
        a[i].pante=calcularepanta(i);
    puncte aux;
    for (int i=1;i<n;i++)
        for (int j=i+1;j<=n;j++)
            if (a[i].pante>a[j].pante)
            {
               aux=a[i];
               a[i]=a[j];
               a[j]=aux;
            }

}
double determinant(int x1,int y1,int z1)
{
    double s1=0;
    s1+=(a[x1].x*a[y1].y);s1+=(a[y1].x*a[z1].y);s1+=(a[x1].y*a[z1].x);
    s1-=(a[y1].y*a[z1].x);s1-=(a[x1].x*a[z1].y);s1-=(a[y1].x*a[x1].y);
    return s1;

}
void afisare()
{
    if (!S.empty())
    {

        int x1=S.top();

        S.pop();
        afisare();
        printf("%.4lf %.4lf\n",a[x1].x,a[x1].y);
    }

}
void rezolvare()
{
    int p1,p2;
    S.push(0);p1=0;
    S.push(1);p2=1;
    for (int i=2;i<=n;i++)
    {
        if (determinant(p1,p2,i)>=0)
        {
            S.push(i);
            p1=p2;
            p2=i;
        }
        else
        {
            S.pop();
            S.push(i);
            p2=i;
        }
    }
    printf("%d\n",S.size());
//    printf("%.4lg %.4lg\n",a[0].x,a[0].y);
    afisare();

}

int main()
{
    citire();
    freopen("infasuratoare.out","w",stdout);
    rezolvare();
    return 0;
}