#include <fstream>
#include <algorithm>
#include <iomanip>
#define e 0.000000000001
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
int n,i,j,Max,vf;
struct punct
{
    double x,y;
}s[120100],v[120100],aux;
double panta(punct a, punct b, punct c)
{
    return (c.y-a.y)*(b.x-a.x)-(b.y-a.y)*(c.x-a.x);
}
double cmp(punct a,punct b)
{
    return panta(v[1],a,b)<0;
}
int main()
{
   fin>>n;
   for(i=1;i<=n;i++)
   {
       fin>>v[i].x>>v[i].y;
       if(v[i].x<v[Max].x || i==1)
       {
           Max=i;
       }
        else
       {
           if(v[Max].x-v[i].x<e)
            if(v[i].y<v[Max].y)
           {
               Max=i;
           }
       }
   }
   aux=v[Max];
   v[Max]=v[1];
   v[1]=aux;
   sort(v+2,v+1+n,cmp);
   s[1]=v[1];
   s[2]=v[2];
   vf=2;
   for(i=3;i<=n;i++)
   {
       while(vf>=1 && panta(s[vf-1],s[vf],v[i])>0)
       {
           vf--;
       }
       vf++;
       s[vf]=v[i];
   }
   fout<<vf<<'\n';
   for(i=vf;i>=1;i--)
   fout<<fixed<<setprecision(6)<<s[i].x<<" "<<s[i].y<<'\n';
    return 0;
}