#include <bits/stdc++.h>

using namespace std;

#define mp make_pair
#define pii pair<int,int>
#define fi first
#define se second

const int nmax = 11;
int q,n;
pii a[nmax];
int main()
{
    cin >> q;
    while(q--)
    {
        bool ok = 1;
        cin >> n;
        for(int i=1; i<=n; i++)cin >> a[i].fi >> a[i].se;
        sort(a+1,a+n+1);
        int d = 0;
        int d1 = -1e9,d2 = -1e9;
        for(int i=1; i<n; i++)
        {
            if(a[i].fi != a[i+1].fi)d++;
            if(d > 2)
            {
                cout << "NO" << endl;
                ok = 0;
                break;
            }
            if(a[i].se != d1)
            {
                if(d1 != -1e9)
                {
                    if(a[i].se != d2)
                        if(d2 == -1e9)d2 = a[i].se;
                        else
                        {
                            cout << "NO" << endl;
                            ok = 0;
                            break;
                        }
                }
                else d1 = a[i].se;
            }
        }
        if(ok)cout << "YES" << endl;
    }
    return 0;
}