def deciphered_index_with_key(index, key):
    """
    Using key to find the deciphered index, which is the original alphabet.
    :param index: int, the index of each char of ciphered string in ALPHABET.
    :param key: int, the secret number to decided how many index position should move to deciphered.
    :return: int, the index been deciphered.
    """
    if index + key > 25:
        return index + key - 26
    return index + key