def get_stream(cipher_text: str, j: int, start: int) -> str:
    """
    Get the stream
    Input:
        cipher_text: the ciphertext we are attempting to decrypt
        j: getting the stream which is every jth letter
        start: letter to start at
    """
    message = ""
    for i in range(start, len(cipher_text), j):
        message += cipher_text[i]
    return message