#include<fstream>
#include<algorithm>
#include<iomanip>
using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
int i,n,K,st[130000],poz,vf;
struct punct
{
    double x,y,panta;
}v[130000],o,aux;
int cmp(punct a,punct b)
{
    if(a.panta==b.panta) return a.x<b.x;
    return a.panta<b.panta;
}
int convex()
{
    punct a,b,c;
    double S;
    a=v[st[vf-1]];
    b=v[st[vf]];
    c=v[i];
    S=(a.x-c.x)*(b.y-a.y)+(a.x-b.x)*(a.y-c.y) ;
    if(S>0) return 1;
    return 0;
}
int main()
{
    f>>n;
    o.x=o.y=9999999;
    for(i=1;i<=n;i++)
    {
        f>>v[i].x>>v[i].y;
        if(v[i].x<o.x||v[i].x==o.x&&v[i].y<o.y) o=v[i],poz=i;
    }
    aux=v[1];
    v[1]=v[poz];
    v[poz]=aux;
    for(i=2;i<=n;i++) v[i].panta=(v[i].y-o.y)/(v[i].x-o.x);
    sort(v+2,v+n+1,cmp);
    st[1]=1; st[2]=2; vf=2;
    for(i=3;i<=n;i++)
    {
       while(!convex()&&vf>2) vf--;
       st[++vf]=i;

    }
    g<<vf<<"\n";
     for(i=1;i<=vf;i++) g<<fixed<<setprecision(6)<<v[st[i]].x<<" "<<fixed<<setprecision(6)<<v[st[i]].y<<"\n";
    return 0;
}