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

public class Solution {
    private static Scanner in;

	public static void main(String[] args) {
        in = new Scanner(System.in);
        int q = in.nextInt();
        for(int ao=0;ao<q;ao++){        	
        	int n = in.nextInt();
        	int x,y;
        	if(n<3){
        		System.out.println("YES");
        		for(int i=0;i<n;i++){
        			x = in.nextInt();y = in.nextInt();
        		}
        	}else{
        		int cnst = 1000000;
        		int x1 = cnst;
        		int y1 = cnst;
        		int x2 = cnst;
        		int y2 = cnst;
        		boolean fx = true;
        		boolean fy = true;
        		for(int i=0;i<n;i++){
            		x = in.nextInt();y = in.nextInt();
        			if(x1==cnst&&x2==cnst){
        				x1 = x;
        			}else if(x2==cnst){
        				if(x!=x1)
        				x2 = x;
        			}else if(x==x1||x==x2){
        			}else{
        				fx = false;
        			}
        			if(y1==cnst&&y2==cnst){
        				y1 = y;
        			}else if(y2==cnst){
        				if(y!=y1)
        				y2 = y;
        			}else if(y==y1||y==y2){
        			}else{
        				fy = false;
        			}
        		}
        		if(fx&&fy){
            		System.out.println("YES");        			
        		}else{
            		System.out.println("NO");       			
        		}
        	}
        }
    }
}