# Enter your code here. Read input from STDIN. Print output to STDOUT

import math
from collections import Counter

q = input()

_ = 0
while _ < q:
    _ += 1
    n = input()
    t = 0
    # a,b = map(int, raw_input().split())
    arrx,arry = [],[]
    nope = False
    while t < n:
        x,y = map(int, raw_input().split())
        arrx.append(x)
        arry.append(y)
        t += 1
        
    countx = Counter(arrx)
    # print countx
    a = countx.most_common(2)
    valx, alx = a[0]
    valx2, alx2 = a[1]
    county = Counter(arry)
    # print arrx
    # print a
    a = county.most_common(2)
    valy, aly = a[0]
    valy2, aly2 = a[1]
    # print arry
    # print a
    # for each in range(len(arrx)):
    each = 0
    while each < n:
        if arrx[each] != valx and arrx[each] != valx2  and arry[each] != valy2 and arry[each] != valy:
            nope = True
            break
        each += 1
    if nope:
        print "NO"
    else:
        print "YES"