def from_digits(digits, base):
    return sum(n * base ** i for i, n in enumerate(reversed(digits)))


def to_digits(number, base_to):
    result = []
    while number > 0:
        result.append(number % base_to)
        number //= base_to
    return result[::-1]  # list(reversed(result))


def rebase(from_base, digits, to_base):
    if (from_base < 2):
        raise ValueError("Invalid input base.")

    if (to_base < 2):
        raise ValueError("Invalid output base.")

    if any(True for d in digits if d < 0 or d >= from_base):
        raise ValueError("Invalid input digit.")

    return to_digits(from_digits(digits, from_base), to_base)