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 sc = new Scanner(System.in);
        int q = sc.nextInt();
        while(q>0)
        {
            int n = sc.nextInt();
            int a[] = new int[n];
            int b[] = new int[n];
            for(int i = 0; i < n; i++)
            {
                 a[i] = sc.nextInt();
                 b[i] = sc.nextInt();
            }
            int flag1 = 0;
            for(int i = 0; i < n; i++)
            {
                flag1 = 0;
                for(int j = 0; j < n;j++)    
                {
                    if(a[i] == a[j] && i != j)    
                    {
                        for(int k = i; k < n; k++)
                        {
                            for(int l = 0; l < n;l++)    
                            {
                                if(b[k] == b[l] && k != l)    
                                {
                                     flag1 = 1;      
                                }
                             }
                        }               
                    }
                }
                if(flag1 == 0)
                {
                    break;
                }
            }
            if(flag1 == 0)
            {
                System.out.println("NO");    
            }else{
                System.out.println("YES");    
            }
            q--;    
        }
    }
}