#include <iostream>
#include <cmath>
#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
int n,k;
struct punct{double x;double y;}p[120003];
punct S[120003];

double det(punct a, punct b, punct c){
 return ((a.x*b.y)+(b.x*c.y)+(a.y*c.x)-(b.y*c.x)-(a.x*c.y)-(b.x*a.y));
}
bool comp(punct i,punct j){
   double D;
   D=det(p[1],i,j);
   if(D>0) return true;
   return false; }


int main()

{int i,j;
    f>>n;
 f>>p[1].x>>p[1].y;
    j=1;
   for(i=2;i<=n;i++){
    f>>p[i].x>>p[i].y;
     if(p[i].x<p[j].x || (p[i].x==p[j].x && p[i].y<p[j].y)) j=i;
   }

swap(p[1],p[j]);
sort(p+2,p+1+n,comp);
S[1]=p[1];S[2]=p[2];k=2;
for(i=3;i<=n;i++){
    while(k>1 && det(S[k-1],S[k],p[i])<0)k--;
    k++; S[k]=p[i];
}
g<<k<<'\n';
g<<fixed;
 for(i=1;i<=k;i++) g<<setprecision(6)<< S[i].x<<' '<<setprecision(6)<<S[i].y<<'\n';
     f.close();
    g.close();
    return 0;
}