npoints

// Example program
#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
using namespace std;
  struct po{
   int x;
   int y;
  };
int main()
{
    int n;
    cin>>n;
    vector<po> p;
    vector<int> vid;
  p.resize(n);
  for(int i=0;i<n;i++){
   cin>>p[i].x>>p[i].y;   
  }
  sort(p.begin(),p.end(),[](const po &left,const po &right){
   if(left.y!=right.y){
    return left.y<right.y;   
   }
   return left.x<right.x;
  });
  p.erase(unique(p.begin(),p.end(),[](const po &left,const po &right){
  return left.x==right.x && left.y==right.y;
}),p.end());
n=p.size();
if(n==1){
cout<<0;
return 0;
}
int next;
double dx=-1,dy=0;
  int cur=0;
  vid.push_back(cur);
  while(true){
   int next=-1;
   double bestcos=-99;
  for(int i=0;i<n;i++){
  double cosi;
  if(i!=cur){
    int ndx=p[i].x-p[cur].x;
    int ndy=p[i].y-p[cur].y;
    cosi=(dx*ndx+dy*ndy)/sqrt(ndx*ndx+ndy*ndy) ;
  
  if(cosi>bestcos){
    next=i;
    bestcos=cosi;
  }
  }
  }
  dx=p[next].x-p[cur].x;
  dy=p[next].y-p[cur].y;
  double len=sqrt(dx*dx+dy*dy);
  dx/=len;
  dy/=len;
  cur=next;
  
  if(cur==0){
  vid.push_back(cur);
  break;
    
  }
    vid.push_back(cur);

 
  }
    
  
  
    for(int i=0;i<vid.size();i++){
     cout<<p[vid[i]].x<<" "<<p[vid[i]].y<<endl;
    }
  
  }