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


int main() {
    int q;
    cin >> q;
    while(q > 0){
        int n;
        cin >> n;
        vector <int> xs = vector<int>(n);
        vector <int> ys = vector<int>(n);
        int x1,y1,x2,y2;
        for(int i = 0;i < n;i++)
            cin >> xs[i] >> ys[i];
        x1 = xs[0];
        x2 = xs[1];
        
        y1 = ys[0];
        y2 = ys[1];
        bool err = false;
        for(int i = 2;i < n;i++){
            if(x1 == x2 && x1 != xs[i])
                x1 = xs[i];
            else if(x1 != x2 && x1 != xs[i] && x2 != xs[i])
                err = true;
            
            if(y1 == y2 && y1 != ys[i])
                y1 = ys[i];
            else if(y1 != y2 && y1 != ys[i] && y2 != ys[i])
                err = true;
            
        }
        if(err)
            cout << "NO";
        else 
            cout << "YES";
        cout << endl;
        q--;
    }
    return 0;
}