def get_keys() -> list:
    """Get route cipher keys from user.

    User only has to enter positive/negative integers. Each gets added to a
    list and returned when the user has no other keys to add.

    Returns:
        List of integers as column numbers and positive/negative values as
        route direction.

    """
    cols = int(input('How many columns? '))
    keys = []
    while len(keys) < cols:
        key = int(input('Enter a signed integer key: '))
        keys.append(key)
    print(f'\nThis is the route cipher key: {keys}\n')
    return keys