#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>

int main()
{
    int q,n;
    int x,y;
    scanf("%d",&q);
    while(q--)
    {
        scanf("%d",&n);
        int arr[10];
        int count=-1;
        int count1=0;
        int out=0;
        while(n--)
        {
            scanf("%d%d",&x,&y);
            if(count==-1)
            {
                arr[0]=x;
                count++;
                continue;
            }
            if(x==arr[0])
                continue;
            if(x!=arr[0] && count1==0)
            {
                arr[1]=x;
                count1=1;
                continue;
            }
            if(x!=arr[0] && x!=arr[1])
                out=1;
        }
        if(out==1)
                printf("NO\n");
        else
                printf("YES\n");
    }
    return 0;
}