#include<iomanip>
#include <fstream>
#include<algorithm>
using namespace std;
struct punct {
double x,y;
}v[120001],x;
int n,i,p,st[120001],vf;
int arie(punct a, punct b, punct c){
  double kk=(b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x);

  if(kk<=0)
    return -1;
  return 1;
  }
int cmp(struct punct a, struct punct b){
return arie(v[1],a,b)<0;
}
double minx,miny;

  ifstream f("infasuratoare.in");
  ofstream g("infasuratoare.out");
int main()
{
f>>n;
f>>v[1].x>>v[1].y;
minx=v[1].x;miny=v[1].y;p=1;
for(i=2;i<=n;i++)
    {
    f>>v[i].x>>v[i].y;
    if(minx>v[i].x)
           {minx=v[i].x;
             p=i;
           }
    else
    if(minx==v[i].x&&miny>v[i].y){
        miny=v[i].y;
        p=i;
    }

    }
 x=v[p]; v[p]=v[1]; v[1]=x;
sort(v+2,v+n+1,cmp);
st[1]=1;st[2]=2;
vf=2;
for(i=3;i<=n;i++){
    while(vf>=2&&arie(v[st[vf-1]],v[st[vf]],v[i])>0)
     vf--;
   vf++;
   st[vf]=i;
}
g<<vf<<'\n';
g<<fixed;
for(i=vf;i>=1;i--)
    g<<setprecision(6)<<v[st[i]].x<<" "<<v[st[i]].y<<'\n';
    return 0;
}