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


int main() {

    int number_of_queries, num_points_current_query, curr_x, curr_y, temp, no_set;
    set<int> x_coords, y_coords;
    string input_pair;
    
    cin >> number_of_queries;
    
    for (int a = 0; a < number_of_queries; a++) {
        cin >> num_points_current_query;
        if (num_points_current_query < 4) {
            cout << "YES" << endl;
            for (int c = 0; c < num_points_current_query; c++) {
                cin >> temp;
                cin >> temp;
            }
            continue;
        }
        else {
            for (int b = 0; b < num_points_current_query; b++) {
                no_set = 0;
                cin >> curr_x;
                cin >> curr_y;
                if (b < 3) {
                    x_coords.insert(curr_x);
                    y_coords.insert(curr_y);
                }
                else {
                    if (x_coords.count(curr_x) == 0 && y_coords.count(curr_y) == 0) {
                        cout << "NO" << endl;
                        no_set = 1;
                        break;
                    }
                }
                
            }
            if (no_set == 0) {
                cout << "YES" << endl;
            }
        }
        
        
    }
        
    
    return 0;
}