import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        BufferedReader in = null;
        long answer = 0;
        int queries = 0;
        try {
            
            in = new BufferedReader(new InputStreamReader(System.in));
            queries = Integer.parseInt(in.readLine());
            int points = 0;
            for (int i = 0; i < queries; i++) {
                points = Integer.parseInt(in.readLine());
                String[] pointArr = in.readLine().split(" ");
                int x = Integer.parseInt(pointArr[0]);
                int y = Integer.parseInt(pointArr[1]);
                boolean yes = true;
                for (int j = 1; j < points; j++) {
                    String[] mPointArr = in.readLine().split(" ");
                    if ((Integer.parseInt(mPointArr[0]) != x) && (Integer.parseInt(mPointArr[1]) != y)) {
                        yes = false;
                        break;
                    }
                }
                if (yes) System.out.println("YES");
                else System.out.println("NO");
            }
            
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                in.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
                
        }
        
    }
}