#include <fstream>
#include <vector>
#include <algorithm>
#include <iomanip>
#define double long double
#define int long long

using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

vector< pair <double, double>> v, hull1, hull2;

vector< pair< double, double>> convex_hull(vector< pair< double, double>>);
int convex(pair<double, double>, pair<double, double>, pair<double, double>);

signed main()
{
  int i, n;
  double a, b;
  fin>>n;
  for(i=1; i<=n; i++)
  {
    fin>>a>>b;
    v.push_back(make_pair(a, b));
  }
  hull1=convex_hull(v);
  reverse(v.begin(), v.end());
  hull2=convex_hull(v);
  fout<<hull1.size()+hull2.size()<<'\n';
  for(auto i:hull1) fout<<fixed<<setprecision(12)<<i.first<<' '<<i.second<<'\n';
  for(auto i:hull2) fout<<fixed<<setprecision(12)<<i.first<<' '<<i.second<<'\n';
}

int convex(pair<double, double> a, pair<double, double> b, pair<double, double> c)
{
   return (b.first-a.first)*(c.second-a.second)-(b.second-a.second)*(c.first-a.first);
}

vector< pair< double, double>> convex_hull(vector< pair< double, double>> v)
{
  pair< double, double> p1, p2;
  vector< pair< double, double>> hull;
  hull.clear();
  sort(v.begin(), v.end());
  for(auto i:v)
  {
    while(hull.size()>=2)
    {
      p1=hull[hull.size()-2];
      p2=hull[hull.size()-1];
      if(convex(p1, p2, i)<=0) break;
      hull.pop_back();
    }
    hull.push_back(i);
  }
  hull.pop_back();
  return hull;
}