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 row=-1;
        int col=-1;
        int flag=-1;
        for(int a0 = 0; a0 < n; a0++){
            int flagTemp=-1;
            int rowTemp = in.nextInt();
            int colTemp = in.nextInt();
            if(a0==0){
                row=rowTemp;
                col=colTemp;
                    
            }
            else{
                      if(rowTemp!=row & colTemp!=col){
                    System.out.println("NO");
                    return;
                }
                if(a0==1){
                     if(rowTemp==row & colTemp!=col){
                    flag=0;
                }
                 if(colTemp==col & rowTemp!=row){
                    flag=1;
                }
                    
                }
                
          
                if((rowTemp==row & colTemp!=col &  flag==0 )|(colTemp==col & rowTemp!=row &  flag==1)){
                   continue;
                }
                else{
                      System.out.println("NO");
                   return;
                }
                
            }
            
        }
         System.out.println("YES");
    }
}