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


int main() {
    long q;
    cin >>q;
    for(long i=0;i<q;i++){
        long n;
        vector <pair<long,long>> G(n);
        for(long j=0;j<n;j++){
            long x,y;
            cin >> x >>y;
            G[j]=make_pair(x,y);        
        }
        
        bool k=true;
        for(long p=0;p<n-1;p++){
            for(long q=0;q<n;q++){
                if(G[p].first!=G[p].first && G[p].second!=G[q].second){
                    k=false;
                    break;
                }
            }           
        }
        cout << (k?"YES":"NO") << endl;
        
    }
    return 0;
}