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def aliquot_sum(input_num: int) -> int:

"""

Finds the aliquot sum of an input integer, where the

aliquot sum of a number n is defined as the sum of all

natural numbers less than n that divide n evenly. For

example, the aliquot sum of 15 is 1 + 3 + 5 = 9. This is

a simple O(n) implementation.

@param input_num: a positive integer whose aliquot sum is to be found

@return: the aliquot sum of input_num, if input_num is positive.

Otherwise, raise a ValueError

Wikipedia Explanation: https://en.wikipedia.org/wiki/Aliquot_sum

>>> aliquot_sum(15)

>>> aliquot_sum(6)

>>> aliquot_sum(-1)

Traceback (most recent call last):

...

ValueError: Input must be positive

>>> aliquot_sum(0)

Traceback (most recent call last):

...

ValueError: Input must be positive

>>> aliquot_sum(1.6)

Traceback (most recent call last):

...

ValueError: Input must be an integer

>>> aliquot_sum(12)

>>> aliquot_sum(1)

>>> aliquot_sum(19)

"""

if not isinstance(input_num, int):

raise ValueError("Input must be an integer")

if input_num <= 0:

raise ValueError("Input must be positive")

return sum(

divisor for divisor in range(1, input_num // 2 + 1) if input_num % divisor == 0

)

if __name__ == "__main__":

import doctest

doctest.testmod()

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