import java.io.*;
import java.util.*;

public class Solution {

    public static void main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
      
        Scanner in = new Scanner(System.in) ;
    
    int q = in.nextInt() ;
    
    for( int i = 0 ; i < q ; i++ ){
        
        int n = in.nextInt() ;
        
        boolean flag = true ;
        int x , y ;
        
        x = y = 0 ;
        
        int[][] pts = new int[n][2] ;
        
        int[] xA = new int[2] ;
        int[] yA = new int[2] ;
        
        for( int j = 0 ; j < n ; j++ ){
            
            pts[j][0] = in.nextInt() ;
            pts[j][1] = in.nextInt() ;
            
        }
        
        for( int j = 0 ; j < n ; j++ ){
            
            if( x == 0 ){
                xA[0] = pts[j][0] ;
                x++ ;
            }
            else if( x == 1 ){
                if( xA[0] != pts[j][0] ){
                    xA[1] = pts[j][0] ;
                    x++ ;
                }
            }
            else if( x == 2 ){
                if( xA[0] != pts[j][0]  && xA[1] != pts[j][0] )
                    flag = false ;
                    break ;
            }
            
            if( y == 0 ){
                yA[0] = pts[j][1] ;
                y++ ;
            }
            else if( y == 1 ){
                if( yA[0] != pts[j][1] ){
                    yA[1] = pts[j][1] ;
                    y++ ;
                }
            }
            else if( y == 2 ){
                if( yA[0] != pts[j][1]  && yA[1] != pts[j][1] ){
                    flag = false ;
                    break ;
                }
            }
                
                  
        }
        
        
        if( flag )
            System.out.println("YES") ;
        else
            System.out.println("NO") ;
        
        
    }
        
    }        
}