import math


def add_line_numbers(code: str) -> str:
    lines = code.splitlines()
    if not lines:
        return code  # empty anyway

    # cannot use math.ceil() here bc lg100=2
    max_digits = math.floor(math.log10(len(lines))) + 1

    for n, l in enumerate(lines, 1):
        digits_in_n = math.floor(math.log10(n)) + 1
        spaces_before_number = max_digits - digits_in_n
        lines[n - 1] = " " * spaces_before_number + str(n) + " " + l

    return "\n".join(lines)