import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        boolean vertical=false;
        boolean horizontal=false;
        boolean flag=true;
        int prevX=-100;int prevY=-100;
        for(int a0 = 0; a0 < n; a0++){
            int x = in.nextInt();
            int y = in.nextInt();
            if(prevX==-100){ prevX=x;prevY=y;}
            else if(prevX==x && !vertical) horizontal=true;
            else if(prevY==y && !horizontal) vertical=true;
            else if(prevX==x && vertical){
                System.out.println("NO");flag=false;break;
            }
            else if(prevY==y && horizontal){
                System.out.println("NO");flag=false;break;
            }
            else if( prevX!=x && prevY!=y){
                System.out.println("NO");flag=false;break;
            }
            
        }
        if(flag){
            System.out.println("YES");                
        }
        
    }
}