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


int main() {
    int q,n,k;
    cin>>q;
    int count=0;
    for(int i=0;i<q;i++)
    {
        cin>>n;
        int x[n],y[n];
        for(int j=0;j<n;j++)
        {
            cin>>x[j]>>y[j];   
        } 
        if(n==1 || n==2 || n==3)
        {
            cout<<"YES"<<endl;
            continue;
        }    
        for(k=1;k<n;k++)
        {
            if(x[k]!=x[0] && y[k]!=y[0])
             {
                for(int l=1;l<n;l++)
                 {
                    if(x[l]!=x[0] && y[l]!=y[0] && x[l]!=x[k] && y[l]!=y[k])   
                    {     cout<<"NO"<<endl;
                            count++;
                            break;
                    }
                }
                break;
            }   
                
        } 
        if(count==0)
            cout<<"YES"<<endl;
        count=0;
        
    } 
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    return 0;
}