from collections import Counter

for _ in range(int(input())):
    n = int(input())
    rectx = Counter()
    all_points = []
    for i in range(n):
        x, y = map(int, input().split())
        rectx.update([x])
        all_points.append((x, y))

    xs = rectx.most_common()[0]
    indice = 0
    for i in range(xs[1]):
        if all_points[indice][0] == xs[0]:
            del all_points[indice]
        else:
            indice += 1


    if not all_points:
        print("YES")
    else:
        y = all_points[0][1]
        for element in all_points:
            if element[1] != y:
                print("NO")
                break
        else:
            print("YES")