#include <map>
#include <set>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <string>
#include <bitset>
#include <cstdio>
#include <limits>
#include <vector>
#include <climits>
#include <cstring>
#include <cstdlib>
#include <fstream>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <unordered_map>

using namespace std;


int main(){
    int n;
    cin >> n;
    int x1;
    int y1;
    int counter =0;
    for(int a0 = 0; a0 < n; a0++){
        int x;
        int y;
        cin >> x >> y;
        if(counter==0){
            x1 =x;
            y1 =y;
            counter =1;
        }
        
        if(x == x1 && counter ==1 && a0!=0 ){
           counter =2;
        }
        else if(y == y1 && counter ==1 && a0!=0){
           counter =3;
           
        }
        else if(counter ==1 && a0!=0){
            cout<<"NO"<<endl;
            return 0;
        }
        
        if(x == x1 && counter ==2 && a0>1){
            counter =2;
        }
        else if(y == y1 && counter ==3 && a0>1){
           counter =3; 
        }
        else if(a0>1){
           counter =4;
           cout<<"NO"<<endl;
           return 0;
 
        }
        if(a0==n-1){
            cout<<"YES"<<endl;
        }
        
    }
    
    return 0;
}