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();
        int i,j,c,n,a1,a2,b1,b2;
        
        while(q>0)
           {
            c=0;
            n=in.nextInt();
            int ar[][]=new int[2][n];
            
            for(i=0;i<n;i++)
                {
                
                ar[0][i]=in.nextInt();
                ar[1][i]=in.nextInt();
                
            }
            if(n==1||n==2)
                {System.out.println("YES");}
            else
                {
                for(i=0;i<n;i++)
                    {
                    for(j=0;j<n;j++)
                        {
                        if(i!=j)
                            {
                        if((ar[0][i]==ar[0][j])||(ar[0][i]==ar[1][j])||(ar[1][i]==ar[0][j])||(ar[1][i]==ar[1][j]))
                        {break;}}
                    }
                    if(j==n)
                        {c=1;
                        break;}
                }
                if(c==1)
                    {System.out.println("NO");}
                else{System.out.println("YES");}
            }
            
        q--;} 
    }
}