def encrypt_message(
    message: str, alphabet: str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ.", period: int = 5
) -> str:
    message, alphabet, character_to_number, number_to_character = __prepare(
        message, alphabet
    )
    encrypted, encrypted_numeric = "", ""

    for i in range(0, len(message) + 1, period):
        encrypted_numeric += __encrypt_part(
            message[i : i + period], character_to_number
        )

    for i in range(0, len(encrypted_numeric), 3):
        encrypted += number_to_character[encrypted_numeric[i : i + 3]]

    return encrypted