from itertools import cycle

def make_cipher(key):
    'Build monoalphabetic substitution list.'
    seed = list(dict.fromkeys(key)) # remove duplicate letters
    # build columns
    cols = [[c] for c in seed]
    col_it = cycle(cols)
    for c in map(chr, range(ord('A'), ord('Z') +1)):
        if c not in seed:
            next(col_it).append(c)
    # sort columns
    cols.sort()
    # join all
    return ''.join(''.join(col) for col in cols)

def encrypt(key, plain):
    cipher = make_cipher(key)
    encrypt1 = (lambda c:   ' ' if c == ' ' 
                            else cipher[ord(c)-ord('A')] )
    return ''.join(map(encrypt1, plain))

def decrypt(key, crypt):
    cipher = make_cipher(key)
    decrypt1 = (lambda c:   ' ' if c == ' ' 
                            else chr(ord('A')+cipher.index(c)) )
    return ''.join(map(decrypt1, crypt))

if __name__ == '__main__':
    n = int(input())
    for _ in range(n):
        print(decrypt(input(), input()))