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


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int q;
    cin>>q;
    while(q--){
        int n;
        cin>>n;
        int xrr[n];
        int yrr[n];
        //map<int,int> m;
        for(int i=0;i<n;i++){
            cin>>xrr[i];
            cin>>yrr[i];
        }
        if(n<4) cout<<"YES"<<endl;
        else{
            int x1,x2=-1,y1,y2=-1;
            x1 = xrr[0];
            y1 = yrr[0];
            bool ans = 0;
            for(int i=1;i<n;i++){
                if(xrr[i]!=x1 && xrr[i]!=x2){
                    if(x2==-1) x2 = xrr[i];
                    else if(xrr[i]!=x2){
                        cout<<"NO"<<endl;
                        ans = 1;
                        break;
                    }
                }
                if(yrr[i]!=y1 && yrr[i]!=y2){
                    if(y2==-1) y2 = yrr[i];
                    else if(yrr[i]!=y2){
                        cout<<"NO"<<endl;
                        ans = 1;
                        break;
                    }
                }
            }
            if(!ans) cout<<"YES"<<endl;
        }
    }
    return 0;
}