using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
class Solution {

    static void Main(String[] args) {
        int n = Convert.ToInt32(Console.ReadLine());
        
        bool horizontal = false;
        int axisValue = 0;
        
        string[] firstTokens = Console.ReadLine().Split(' ');
        int x = Convert.ToInt32(firstTokens[0]);
        int y = Convert.ToInt32(firstTokens[1]);

        string[] secTokens = Console.ReadLine().Split(' ');

        int secondX = Convert.ToInt32(secTokens[0]);
        int secondY = Convert.ToInt32(secTokens[1]);
        
        if(secondX == x) //vertical
        {
            horizontal = false;
            axisValue = x;
        }
        else if(secondY == y) //horizontal
        {
            horizontal = true;
            axisValue = y;
        }
        else 
            goto invalid;
        
        
        for(int a0 = 2; a0 < n; a0++)
        {
            int[] point = Console.ReadLine().Split(' ').Select(s => Convert.ToInt32(s)).ToArray();
            
            if((horizontal && point[1] != axisValue) || 
                (!horizontal && point[0] != axisValue))
            {
                goto invalid;
            }   
        }
        
        Console.WriteLine("YES");
        return;
        
        invalid:
            Console.WriteLine("NO");
    }
}