#include<set>
#include<string>
using namespace std;
int main(){
  set<string> country;  //{}
  country.insert("China");//{"China"}
  return 0;
}

#include<set>
#include<string>
using namespace std;
int main(){
  set<string> country;         //{}
  country.insert("China");     //{"China"}
  country.erase("China");      //{}
  return 0;
}

#include<set>
#include<string>
#include<stdio.h>
int main(){
  set<string> country;
  country.insert("China");
  if(country.count("China")){
    cout<< "China belong to country" << endl;
  }
  return 0;
}

//set<T>::iterator it
#include<set>
#include<string>
#include<iostream>
using namespace std;
int main(){
  set<string> country;
  country.insert("China");
  country.insert("America");
  country.insert("France");
  for(set<string>::iterator it=country.begin(); it !=country.end();it++){
    cout<<*it<<endl;
  }
  return 0;
}

#include<iostream>
#include<set>
using namespace std;
struct Point{
  int x,y;
  bool operator <(const Point &rhs)const{
    if(x==rhs.x){
      return y<rhs.y;
    }else{
      return x<rhs.x;
      }
  }
};
int main(){
  int n;
  set<Point> v;
  cin>>n;
  for(int i=0;i<n;i++){
    Point temp;
    cin >>temp.x >> temp.y;
    v.insert(temp);
  }
  for(set<Point>::iterator it=v.begin(); it!=v.end();it++){
    cout<<it->x<<" "it->y<<endl;
  }
}