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


int main() {
   int q; cin >> q;
    while (q--) {
        int n; cin >> n; int rows[n]; int cols[n];
        vector<int> disctrow; vector<int> disctcol;
        for (int i = 0; i < n; i++) {
            cin >> rows[i];
            bool foundr = 0;
            for (int j = 0; j < disctrow.size(); j++) {
              if (disctrow[j] == rows[i])  foundr = 1;
            }
            if (!foundr) disctrow.push_back(rows[i]);
            cin >> cols[i];
            bool foundc = 0;
            for (int j = 0; j < disctcol.size(); j++) {
              if (disctcol[j] == cols[i])  foundc = 1;
            }
            if (!foundc) disctcol.push_back(cols[i]);
        }
        if (disctcol.size() > 2 || disctrow.size() > 2) cout << "NO\n";
        else cout << "YES\n";
        
        
    }
   // system("pause");
}