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) {
        boolean firstTime = true;
        Scanner in = new Scanner(System.in);
        
        int n = in.nextInt();
        int[][] temp = new int[n][2];
        for(int a0 = 0; a0 < n; a0++){
            int x = in.nextInt();
            int y = in.nextInt();
            
                temp[a0][0] = x;
                temp[a0][1] = y;
            
            
            
        }
        boolean vertical = false;
        boolean horizontal = false;
        for(int i=0; i<n-1; i++) {
            if(temp[i][0] == temp[i+1][0]) {
                //Its vertical.
                vertical = true;
            }    
            else if(temp[i][1] == temp[i+1][1]) {
                //horizontal
                horizontal = true;
            }
            else {
                System.out.println("NO");
                vertical = true; horizontal = true;
                break;
            }
            if(vertical == true && horizontal == true) {
                System.out.println("NO");
                break;
            }
            
        }
        if((vertical == false && horizontal == true )|| (vertical == true && horizontal == false))
            System.out.println("YES");
    }
}