#include<bits/stdc++.h>
using namespace std;
#define fastScan ios_base::sync_with_stdio(0); cin.tie(NULL);
#define fill(a,x) memset(a,x,sizeof(a))
#define ll long long int
#define MAX 211
#define MOD 1000000007
#define pii pair<int,int>
#define pll pair<ll,ll>
#define mb make_pair
#define pb push_back
#define sc(x) scanf("%d",&x)
#define scc(x1,x2) scanf("%d%d",&x1,&x2)
#define sccc(x1,x2,x3) scanf("%d%d%d",&x1,&x2,&x3)
#define pr(x) printf("%d ",x)
#define rep(i,n) for(int i=0;i<n;i++)
#define repp(i,a,b) for(int i=a;i<=b;i++)
#define reff(i,a,b) for(int i=a;i>=b;i--)
#define IT(x) for(__typeof (x.begin()) it = x.begin(); it != x.end (); it++)
#define F first
#define S second
#define co cout<<"vai"<<endl;
#define coo cout<<"yt"<<endl;
#define dbg(a)         std::cerr<<#a<<"="<<(a)<<"\n"
#define dbg1(a,b)       std::cerr<<#a<<"="<<(a)<<", "<<#b<<"="<<(b)<<"\n"
#define dbg2(a,b,c)     std::cerr<<#a<<"="<<(a)<<", "<<#b<<"="<<(b)<<", "<<#c<<"="<<(c)<<"\n"
#define dbg3(a,b,c,d)   std::cerr<<#a<<"="<<(a)<<", "<<#b<<"="<<(b)<<", "<<#c<<"="<<(c)<<", "<<#d<<"="<<(d)<<"\n"
#define dbg4(a,b,c,d,e) std::cerr<<#a<<"="<<(a)<<", "<<#b<<"="<<(b)<<", "<<#c<<"="<<(c)<<", "<<#d<<"="<<(d)<<", "<<#e<<"="<<(e)<<"\n"
const int INF = 2034567891;
const ll INF64 = 1234567890123456789ll;
int dx[] = { 1,-1,0,0,1,-1,-1,1 };
int dy[] = { 0,0,1,-1,-1,-1,1,1 };
ll power(ll x,ll y)
{
    ll ans=1;
    while(y>0){
        if(y&1)
            ans=(ans*x)%MOD;
        x=(x*x)%MOD;
        y/=2;
    }
    return ans;
}
int main()
{
	 ll q,n;
	 cin>>q;
	 while(q--)
	 {
	 	cin>>n;
	 	ll x[n],y[n];
	 	pll a[n];
	 	rep(i,n)
	 	{
	 	 cin>>a[i].F>>a[i].S;
	    }
	 	sort(a,a+n);
	 	if(n<=3)
	 	cout<<"YES"<<endl;
	    else
	 	{
		  ll fl=0;
		  set<ll>s;
		  set<ll>::iterator it;
		  rep(i,n)
		  {
		  	 it=s.find(a[i].F);
		  	 if(it!=s.end())
		  	 continue;
		  	  s.insert(a[i].F);
		  	 if(s.size()>2)
		  	 {
		  	   fl=1;
				 break;	
			 }
			 
			
		  }
		  s.clear();
		  rep(i,n)
		  {
		  	 it=s.find(a[i].S);
		  	 if(it!=s.end())
		  	 continue;
		  	 s.insert(a[i].S);
		  	 if(s.size()>2)
		  	 {
		  	     fl=1;
				 break;	
			 }
			
			 
		  }
//		  for(auto it :s)
//		  cout<<it<<endl;
		  if(fl==0)
		  cout<<"YES"<<endl;
		  else
	 	cout<<"NO"<<endl;
	 }
   }
}