import java.io.*;
import java.util.*;

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. */
        Scanner scan = new Scanner(System.in);

		// number of queries 
		int q = scan.nextInt();
		
		for (int i = 0; i < q; i++) {
			
			//number of points in the query
			int n = scan.nextInt();
			
			int x = scan.nextInt();
			int y = scan.nextInt();
			
			for (int j = 0; j < n-1; j++) {
				int x1 = scan.nextInt();
				int y1 = scan.nextInt();
				
				if (x != x1 && y != y1){
					System.out.println("NO");
					return;
				}
			}
			
			System.out.println("YES");
		}
    }
}