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();
        int bigX = in.nextInt();
        int bigY = in.nextInt();
        
        
        Boolean vertical = null;
        Boolean horizontal = null;
        boolean res = true;
        for(int a0 = 1; a0 < n; a0++){
            int x = in.nextInt();
            int y = in.nextInt();
            if(vertical == null && horizontal == null){
                if(x == bigX && y != bigY){
                    vertical = true;
                }
                else if(y == bigY && x != bigX){
                    horizontal = true;
                }
                else if(y == bigY && x == bigX){
                    continue;
                }
                else{
                    res = false;
                    break;
                }
            }
            if(vertical != null && vertical && x != bigX){
                 res = false;
                 break;
            }
            if(horizontal != null && horizontal && y != bigY){
                 res = false;
                 break;
            }
        }
        System.out.println(res ? "YES" : "NO");
    }
}