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


int main() {
    int q, n;
    int* arr[2];
    cin >> q;
    while(q--){
        int x1, x2;
        int y1, y2;
        x1 = x2 = y1 = y2 = 100000;
        
        cin >> n;
        arr[0] = new int[n];
        arr[1] = new int[n];
        bool notPossible = false;
        for(int i = 0; i < n; i++){
            cin >> arr[0][i] >> arr[1][i];
            if(x1 != arr[0][i] && x2 != arr[0][i]){
                if(x1 == 100000){
                    x1 = arr[0][i];
                }
                else if(x2 == 100000){
                    x2 = arr[0][i];
                }
                else{
                    notPossible = true;
                    break;
                }
            }
            
            if(y1 != arr[1][i] && y2 != arr[1][i]){
                if(y1 == 100000){
                    y1 = arr[1][i];
                }
                else if(y2 == 100000){
                    y2 = arr[1][i];
                }
                else{
                    notPossible = true;
                    break;
                }
            }
        }
        if(notPossible){
            cout << "NO" << endl;
        }
        else{
            cout << "YES" << endl;
        }
    }
    return 0;
}