# include <iostream>
# include <cstdlib>
# include <cstdio>
# include <algorithm>
# include <map>
# define f first
# define s second
using namespace std;
pair <int,int> a[11];
map <int,int> st,pt;
int main ()
{
    int n,m;
    cin >> n;
    for(int i = 1;i <= n;i ++)
    {
        cin >> m;
        st.clear();
        pt.clear();
        for(int i = 1;i <= m;i ++)
        {
            cin >> a[i].f >> a[i].s;
            st[a[i].f] = max(st[a[i].f],a[i].f);
            pt[a[i].s] = max(st[a[i].s],a[i].s);
        }

        sort(a + 1,a + n + 1);
        if(m == 1 || m == 2)
        {
            if(m == 1 || a[1].f != a[n].f  && a[1].f != a[n].s){
            cout << "YES\n" << endl;

            continue;
            }
        }
        if(m == 3 )
        {
            if(a[1].f == a[2].f && a[2].s == a[3].s || a[1].s == a[3].s && a[2].f == a[3].f|| a[1].s == a[2].s && a[2].f == a[3].f|| a[1].f == a[2].f && a[1].s == a[3].s){
                cout << "YES\n";
            continue;
            }
        }
        if(m == 4)
        {
            if(a[1].f == a[2].f && a[2].s == a[4].s && a[3].s == a[1].s && a[3].f == a[4].f){
                cout << "YES\n";
            continue;
            }
        }
        if(m > 4)
        {
            if(a[1].f == st[a[1].f] && pt[st[a[1].f]] == a[4].s && pt[a[3].s] == a[1].s && st[pt[a[3].s]] == a[4].f){
                      cout << "YES\n";
            continue;
            }
        }
        cout << "NO\n" << endl;
    }
}