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 x = in.nextInt();
        int y = in.nextInt();
        int flag = 0;
        int coor = 0;
        int x1 = in.nextInt();
        int x2 = in.nextInt();
        if(x1 != x && x2 !=y)
            flag = 1;
        if(x1 == x){
            int cons = x;
            coor = 0;
        }
        else{
            int cons = y;
            coor = 1;
        }
        
        if(flag == 0){
            for(int i = 2; i < n; i++){
            x1 = in.nextInt();
            x2 = in.nextInt();
            if(x1 != x && coor == 0)
                flag = 1;
            if(x2 != y && coor == 1)
                flag = 1;
        }
        }  
        if(flag == 1)
            System.out.println("NO");
        
        else
            System.out.println("YES");
    }   
    
}