#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int q;
    cin>>q;
    while(q--)
        {
            int pts;
            cin>>pts;
            int x_pt[pts];
            int y_pt[pts];
            for(int i=0;i<pts;i++)
                {   
                    
                    cin>>x_pt[i];
                    
                    cin>>y_pt[i];           
            }
                
        int flag[pts]={};
            for(int i=0;i<pts;i++)
                {   
                    for(int j=0;j<pts;j++)
                        {
                           if(i!=j) 
                               {    if(!(((x_pt[i]==x_pt[j])||(x_pt[i]==y_pt[j]))||((y_pt[i]==x_pt[j])||(y_pt[i]==y_pt[j]))))
                                    { flag[i]++; }
                           }
                }
            }
        int zz=0;
        for(int i=0;i<pts;i++)
            {   if(flag[i]==pts-1)
                 {   zz=1;
                
                 }
            }
        
        if(zz==0)
                cout<<"YES"<<"\n";
        if(zz==1)
            cout<<"NO"<<"\n";
    }
    return 0;
}