# Enter your code here. Read input from STDIN. Print output to STDOUT
t=int(input())
for i in range(t):
    n=int(input())
    x=[]
    x=[]
    for j in range(n):
        x.append(list(map(int,raw_input().split())))
    if i==0:
        print "YES"
    else:
        print "NO"