import java.io.*;
import java.util.*;
class google{
    int value;
    boolean used;
    
    public google newGoogle(){
        this.value = 0;
        this.used = false;
        return this;
    }
}
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 scan = new Scanner(System.in);
        int t = scan.nextInt();
        for(int i=0;i<t;i++){
            int n = scan.nextInt();
            int[][] array = new int[n][2];
            int x1 = Integer.MIN_VALUE, x2 = Integer.MIN_VALUE, y1 = Integer.MIN_VALUE, y2 = Integer.MIN_VALUE;
            boolean flag = true;
            for(int j=0;j<n;j++){
                array[j][0] = scan.nextInt();
                if(x1==Integer.MIN_VALUE) x1 = array[j][0];
                else if(x1!=Integer.MIN_VALUE&&array[j][0]!=x1&&x2==Integer.MIN_VALUE) x2 = array[j][0];
                else{
                    if(array[j][0]!=x1&&array[j][0]!=x1&&array[j][0]!=x2){
                        System.out.println("NO");
                        flag = false;
                        break;
                    }
                }
                array[j][1] = scan.nextInt();
                if(y1==Integer.MIN_VALUE) y1 = array[j][1];
                else if(array[j][1]!=y1&&y1!=Integer.MIN_VALUE&&y2==Integer.MIN_VALUE) y2 = array[j][1];
                else{
                    if(array[j][1]!=y1&&array[j][1]!=y1&&array[j][1]!=y2){
                        System.out.println("NO");
                        flag = false;
                        break;
                    }
                }
            }
            if(flag) System.out.println("YES");
        }
    }
}