#include <fstream>
#include <cmath>
#include <algorithm>
#include <iomanip>
using namespace std;
typedef int var;
struct punct
{
    double x,y;
};
punct a[12005],t[12005];
var minimy,minimx;
bool cmp(punct b,punct c)
{
    if((b.x-minimx)*(c.y-minimy)>(c.x-minimx)*(b.y-minimy))
        return 0;
    else
        return 1;
}
int determinant(punct q,punct w,punct e)
{
    return (q.x*w.y+w.x*e.y+e.x*q.y-e.x*w.y-w.x*q.y-q.x*e.y);
}
int main()
{
    ifstream f("infasuratoare.in");
    ofstream g("infasuratoare.out");
    var n;
    f>>n;
    minimx=1000000015;
    var poz1;
    for(var i=1;i<=n;i++)
    {
        f>>a[i].x;
        f>>a[i].y;
        if(minimx>a[i].x)
        {
            minimx=a[i].x;
            minimy=a[i].y;
            poz1=i;
        }
        else
        {
            if(minimx==a[i].x)
                if(minimy>a[i].y)
                   {
                       minimy=a[i].y;
                       poz1=i;
                   }
        }
    }
    punct aux;
    aux=a[poz1];
    a[poz1]=a[1];
    a[1]=aux;
    sort(a+2,a+n+1,cmp);
    var poz=1;
    minimx=1000000015;
 /*   for(var i=1;i<=n;i++)
    {
        if(minimx>a[i].x)
        {
            minimx=a[i].x;
            minimy=a[i].y;
            poz=i;
        }
        else
        {
            if(minimx==a[i].x)
                if(minimy>a[i].y)
                {
                    minimy=a[i].y;
                    poz=i;
                }
        }
    }*/
    t[0].x=0;
    t[0].y=0;
    t[1]=a[1];
    g<<a[poz].x<<" "<<a[poz].y;
    var k=1;
    for(var i=2;i<=n;i++)
    {
        if(determinant(t[k-1],t[k],a[i])>0)
        {
            while(determinant(t[k-1],t[k],a[i])>0)
                k--;
            k++;
            t[k]=a[i];
        }
        else
        {
            k+=1;
            t[k]=a[i];
        }
    }
  /*  for(var i=1;i<poz;i++)
         if(determinant(t[k-1],t[k],a[i])<0)
        {
            while(determinant(t[k-1],t[k],a[i])<0)
                k--;
            k++;
            t[k]=a[i];
        }
        else
        {
            k+=1;
            t[k]=a[i];
        }*/
    g<<k<<'\n';
    for(var i=k;i>=1;i--)
        g<<setprecision(6)<<fixed<<t[i].x<<" "<<t[i].y<<'\n';
    f.close();
    g.close();
    return 0;
}