#include <fstream>
#include <iomanip>
#include <algorithm>
using namespace std;

ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");

const int NMAX = 12e4;

struct ura{
  double x, y;
}st1[NMAX + 1], st2[NMAX + 1],  v[NMAX + 1], prim, ultim;

double arie(ura a, ura b, ura c){
  return  a.x*b.y + b.x*c.y + c.x*a.y -b.y*c.x -c.y*a.x - a.y*b.x;
}
bool cmp(ura a, ura b){
  if(a.x < b.x){
    return true;
  }else{
    if(a.x == b.x){
      return a.y < b.y;
    }else{
      return false;
    }
  }
}
int main(){
  int n;
  f>>n;
  for(int i = 1;i<=n;i++){
    f>>v[i].x>>v[i].y;
  } 
  sort(v + 1, v + n + 1, cmp);

  prim = v[1], ultim = v[n];
  int sp1 = 1;
  st1[sp1] = prim;
  for(int i = 2;i<=n;i++){
    if(arie(prim, ultim, v[i]) < 0 || (v[i].x == ultim.x && v[i].y == ultim.y)){ //dedesubtul dreptei
      while(sp1 > 1 && arie(st1[sp1 - 1], st1[sp1], v[i])< 0){
        sp1--;
      }
      sp1++;
      st1[sp1] = v[i];
    }
  }
  int sp2 = 1;
  st2[sp2] = ultim;
  for(int i = n - 1;i>=1;i--){
    if(arie(prim, ultim, v[i]) > 0 || (v[i].x == prim.x && v[i].y == prim.y)){
      while(sp2 > 1 && arie(v[i], st2[sp2], st2[sp2 - 1])> 0){
        sp2--;
      }
      sp2++;
      st2[sp2] = v[i];
    }
  }
  g<<sp1 + sp2 - 2<<"\n";
  g<<fixed<<setprecision(6);
  for(int i = 1;i<sp1;i++){
    g<<st1[i].x<<" "<<st1[i].y<<"\n";
  }
  for(int i = 1;i<sp2;i++){
    g<<st2[i].x<<" "<<st2[i].y<<"\n";
  }
  return 0;
}