num_tests = int(input())

for t in range(num_tests):
  enc_words = list(map(str, input().split()))
  dec_word = str(input())

  possible_keys = set()

  for word in enc_words:
    if len(word) == len(dec_word):
      diff = set(map(lambda x:(ord(x[0]) - ord(x[1]) + 26) % 26, zip(word, dec_word)))
      if len(diff) == 1:
        possible_keys = possible_keys.union(diff)

  print("".join(sorted(map(lambda x: chr(x + ord('a')), possible_keys))))
  
ab045334eb405e42c0d19f19ce96f2c4a74a4985
<mask token>

<mask token>
for t in range(num_tests):
    enc_words = list(map(str, input().split()))
    dec_word = str(input())
    possible_keys = set()
    for word in enc_words:
        if len(word) == len(dec_word):
            diff = set(map(lambda x: (ord(x[0]) - ord(x[1]) + 26) % 26, zip
                (word, dec_word)))
            if len(diff) == 1:
                possible_keys = possible_keys.union(diff)
    print(''.join(sorted(map(lambda x: chr(x + ord('a')), possible_keys))))

num_tests = int(input())
for t in range(num_tests):
    enc_words = list(map(str, input().split()))
    dec_word = str(input())
    possible_keys = set()
    for word in enc_words:
        if len(word) == len(dec_word):
            diff = set(map(lambda x: (ord(x[0]) - ord(x[1]) + 26) % 26, zip
                (word, dec_word)))
            if len(diff) == 1:
                possible_keys = possible_keys.union(diff)
    print(''.join(sorted(map(lambda x: chr(x + ord('a')), possible_keys))))

num_tests = int(input())

for t in range(num_tests):
  enc_words = list(map(str, input().split()))
  dec_word = str(input())

  possible_keys = set()

  for word in enc_words:
    if len(word) == len(dec_word):
      diff = set(map(lambda x:(ord(x[0]) - ord(x[1]) + 26) % 26, zip(word, dec_word)))
      if len(diff) == 1:
        possible_keys = possible_keys.union(diff)

  print("".join(sorted(map(lambda x: chr(x + ord('a')), possible_keys))))
  