## https://yukicoder.me/problems/no/2148

import itertools

def solve(N, cd):
    # RGBごとにまとめる
    c_map = {}
    for c, d in cd:
        if c not in c_map:
            c_map[c] = []
        c_map[c].append(d)

    c_array = [valeus for valeus in c_map.values()]    
    if len(c_array) == 1:
        return "YES"

    ok_count = 0
    for p in itertools.combinations(c_array, 2):
        v1 = p[0]
        v2 = p[1]
        v2_set = set(v2)
        for v in v1:
            if v in v2_set:
                ok_count += 1
                break
    if ok_count >= len(c_array) - 1:
        return "YES"
    else:
        return "NO"




def main():
    T = int(input())
    answers = []
    for _ in range(T):
        N = int(input())
        cd = []
        for _ in range(N):
            c, d = input().split()
            cd.append((c, int(d)))
        ans = solve(N, cd)
        answers.append(ans)

    for ans in answers:
        print(ans)


if __name__ == '__main__':
    main()