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

int main(){
    int tc;
    cin >> tc;
    while(tc--){
        map<int,set<int> >mapper;
        int n;
        cin >> n;
        for(int i = 0 ; i < n ;i++){
            int x , y;
            cin >> x >> y;
            mapper[x].insert(i);
            mapper[y].insert(i);
        }
        map<int,set<int> >::iterator it;
        bool found = false;
        for(it = mapper.begin() ;!found && it!=mapper.end() ;it++){
            if(it->second.size()==n)
                found = true;
        }
        if(found)
            cout << "YES";
        else
            cout << "NO";
        cout << endl;
    }

}