#include<bits/stdc++.h>
using namespace std;
typedef long long ll;

int main()
{
    ll q;
    cin >> q;

    map<ll,ll>mp;
    map<ll,ll>cp;
    map<ll,ll>::iterator it;

    while(q--){
        ll n;
        cin >> n;
        ll a,b;
        mp.clear();
        cp.clear();
        for(int i=0; i<n; i++){
            cin >> a >> b;
            mp[a]++;
            cp[b]++;
        }
        ll mx = 0, tx = 0;
        for(it = mp.begin(); it!=mp.end(); it++){
            mx = max(it->second,mx);
        }
        //cout << mx << endl;
        for(it = cp.begin(); it!=cp.end(); it++){
            tx = max(it->second,tx);
        }
        //cout << tx << endl;
        if(((mx+tx)-1)==n)
            cout << "YES\n";
        else
            cout << "NO\n";
    }

    return 0;
}