#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,n,i;
    cin>>q;
    while(q--)
        {int flag=0;
        cin>>n;
        int x[n],y[n];
        cin>>x[1]>>y[1];
        cin>>x[2]>>y[2];
        for( i=3;i<=n;i++)
            {
            cin>>x[i]>>y[i];
            if(!(x[i]==x[1]||x[i]==x[2]||y[i]==y[1]||y[i]==y[2]))
         {       flag=1;
          break;
        }
                
        }
         
         if(i!=n+1)
             cout<<"NO\n";
         else
             cout<<"YES\n";
         
    }
    return 0;
}