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 vh=false;
        int x0 = in.nextInt();
        int y0 = in.nextInt();
                
        if(x0==in.nextInt()) {
            vh=true;
            in.nextInt();
        }
        else if(y0!=in.nextInt()) {
            System.out.println("NO");
            return;
            }
        
        
        for(int a0 = 2; a0 < n; a0++){ 
            if (vh){        
                if (x0!=in.nextInt()){
                    System.out.println("NO");
                    return;
                    }
                in.nextInt();
            }
            else {in.nextInt();
            if (y0!=in.nextInt()){
                System.out.println("NO");
                return;
            }}
        }
         System.out.println("YES");
        
    }
}