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


int main() {
    int Q; cin>>Q;
    
    while(Q--){
        set<int> sa, sb;
        
        int N;  cin>>N;
        while(N--){
            int a, b;   cin>>a>>b;
            sa.insert(a);    sb.insert(b);
        }
        
        if(sa.size()==2 && sb.size()==2)
            cout<<"YES"<<endl;
        else
            cout<<"NO"<<endl;
    }
    
    return 0;
}