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. */
        int q;
        Scanner in = new Scanner(System.in);
        q = in.nextInt();
        for(int i=0; i<q; i++){
            int n = in.nextInt();
            int a = in.nextInt();
            int b = in.nextInt();
            boolean yes = true;
            for(int j=1; j<n; j++){
                int x = in.nextInt();
                int y = in.nextInt();
                if(!(x==a||y==b)){
                    yes = false;
                    break;
                }
            }
            if(yes)
                System.out.println("YES");
            else
                System.out.println("NO");
        }
    }
}