#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    int q;
    cin>>q;
    while(q--)
        {
        int n;
        cin>>n;
        int rect[n][2];
        for(int i = 0;i<n;i++)
            cin>>rect[i][0]>>rect[i][1];
        if(n<4)
            {
            cout<<"YES\n";
            continue;
            }
        int xi = rect[0][0], yi = rect[0][1], xj = rect[1][0], yj = rect[1][1],countx = 1, county  = 1;
        for(int i = 1;i<n;i++)
            {
            int tx = rect[i][0], ty = rect[i][1];
            if(countx==1&&tx!=xi)
            {
                countx++;
                xj = tx;
            }
            if(county==1&&yi!=ty)
                {
                county++;
                yj = ty;
            }
            if(countx>1&&tx!=xi&&tx!=xj)
                {
                countx++;
            }
            if(county>1&&ty!=yi&&ty!=yj)
                {
                county++;
            }
        }
        if(countx>2&&county>2)
            cout<<"NO\n";
        else
            cout<<"YES\n";
    }
    return 0;
}