#include <set>
#include <stdio.h>
using namespace std;


int main() {
    int q, n, x, y;
    
    scanf("%d",&q);
    while(q--){
        set<int> a,b;
        scanf("%d",&n);
        while(n--){
            scanf("%d%d",&x,&y);
            a.insert(x);
            b.insert(y);
        }
        if(a.size()<3 && b.size()<3)
            printf("YES\n");
        else
            printf("NO\n");
    }
    return 0;
}