#include<iostream>
#include<cstdio>
#include<algorithm>
#include<set>
#include<map>
#include<vector>
#include<queue>
#include<utility>
#include<cmath>
#include<cstring>
#include<string>
#include<stack>
#include<deque>
#include<functional>
#include<climits>
#include<iomanip>
#define ll long long
#define pp pair<int,int>
#define ppl pair<ll,ll>
#define fi first
#define se second
#define tcase int t; scanf("%d",&t);
#define For(i,a,b) for(i = a; i < b; i++)
#define pb push_back
#define pq priority_queue
#define ve vector
#define lb lower_bound
#define ub upper_bound
#define bs binary_search
using namespace std;

ll n;
ve<ppl> a;
ppl w,x,y,z;

int main()
{

  tcase;
  while(t--)
    {
      a.clear();
      ll i,j,k,l,fl,sum,count;
      
      cin>>n;
      For(i,0,n)
	{
	  cin>>w.fi>>w.se;
	  a.pb(w);
	}

      if(n == 1)
	{
	  cout<<"YES\n";
	  continue;
	}

      else if(n == 2)
	{
	  if(a[0] != a[1]) cout<<"YES\n";
	  else cout<<"NO\n";
	  continue;
	}

      ll x1,x2,x3,y1,y2,y3;

      x1 = a[0].fi,x2 = a[1].fi,x3 = a[2].fi;
      y1 = a[0].se,y2 = a[1].se,y3 = a[2].se;

      fl = 1;
      For(i,3,n)
	{
	  if(a[i].fi == x1 || a[i].fi == x2 || a[i].fi == x3 || a[i].se == y1 || a[i].se == y2 || a[i].se == y3) continue;
	  else fl = 0;
	}

      if(fl == 1) cout<<"YES\n";
      else cout<<"NO\n";
    }



  return 0;
}