#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <bits/stdc++.h>
using namespace std;


long long int q,n;
map<int,int> r,c;
int t1,t2;
int row,col;

int main() {
    cin>>q;
    while(q--){
        cin>>n;
        
        if(n<=2){
            for(int i=0;i<n;i++){
                cin>>t1>>t2;
            }
            cout<<"YES\n";
        }
        else{
            r.clear();
            c.clear();
            row = col = 0;
            for(int i=0;i<n;i++){
                cin>>t1>>t2;
                if(!r[t1]){
                    if(!c[t2]){
                        r[t1] = 1;
                        row++;
                    }
                }
                if(!c[t1]){
                    if(!r[t1]){
                        c[t2] = 1;
                        col++;
                    }
                }
            }
            if(row>2 || col>2) cout<<"NO\n";
            else cout<<"YES\n";
        }
    }
    return 0;
}