//asfaq//................

#include <bits/stdc++.h>
using namespace std;
int main()
{
    int x,y;
    int TC,q;
    cin >> TC;
    while (TC--){
        cin >> q;
        int p = 1;
        for (int i =0 ;i < q; i++){
            cin >> x >> y;
            if (x>0 && y > 0){
                p=0;
            }
        }
        if (p) cout << "YES" << endl;
        else cout << "NO" << endl;
    }
    return 0;
}