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) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        Scanner sc = new Scanner(System.in);
	        int q = sc.nextInt();
	        for(int i = 0 ; i < q ; i++){
	            int n = sc.nextInt();
	            int point[][] = new int[n][2];
	            for(int j = 0 ; j < n ; j++){
	                point[j][0] = sc.nextInt();
	                point[j][1] = sc.nextInt();
	            }
	            int x1 = point[0][0] , y1 = point[0][1],k=1;
	            int x2 = 0 , y2 = 0 ;
	            for(int l = 0 ; l < n ; l++){
	            	if(point[l][0]!=x1){
	            		x2 = point[l][0];
	            		y2 = point[l][1];
	            		break;
	            	}
	            }
	            for( ; k < n ; k++){
	                if(!(point[k][0] == x1 || point[k][1] == y1 || point[k][0] == x2 || point[k][1] == y2)){
	                    System.out.println("NO");
	                    break;
	                }
	            }
	            if(k==n){
	                System.out.println("YES");
	            }
	        }
    }
}