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"""

Problem:

The prime factors of 13195 are 5,7,13 and 29. What is the largest prime factor

of a given number N?

e.g. for 10, largest prime factor = 5. For 17, largest prime factor = 17.

"""

import math

def isprime(num: int) -> bool:

"""Returns boolean representing primality of given number num.

>>> isprime(2)

True

>>> isprime(3)

True

>>> isprime(27)

False

>>> isprime(2999)

True

>>> isprime(0)

Traceback (most recent call last):

...

ValueError: Parameter num must be greater or equal to two.

>>> isprime(1)

Traceback (most recent call last):

...

ValueError: Parameter num must be greater or equal to two.

"""

if num <= 1:

raise ValueError("Parameter num must be greater or equal to two.")

if num == 2:

return True

elif num % 2 == 0:

return False

for i in range(3, int(math.sqrt(num)) + 1, 2):

if num % i == 0:

return False

return True

def solution(n: int = 600851475143) -> int:

"""Returns the largest prime factor of a given number n.

>>> solution(13195)

>>> solution(10)

>>> solution(17)

>>> solution(3.4)

>>> solution(0)

Traceback (most recent call last):

...

ValueError: Parameter n must be greater or equal to one.

>>> solution(-17)

Traceback (most recent call last):

...

ValueError: Parameter n must be greater or equal to one.

>>> solution([])

Traceback (most recent call last):

...

TypeError: Parameter n must be int or passive of cast to int.

>>> solution("asd")

Traceback (most recent call last):

...

TypeError: Parameter n must be int or passive of cast to int.

"""

try:

n = int(n)

except (TypeError, ValueError):

raise TypeError("Parameter n must be int or passive of cast to int.")

if n <= 0:

raise ValueError("Parameter n must be greater or equal to one.")

max_number = 0

if isprime(n):

return n

while n % 2 == 0:

n //= 2

if isprime(n):

return n

for i in range(3, int(math.sqrt(n)) + 1, 2):

if n % i == 0:

if isprime(n / i):

max_number = n / i

break

elif isprime(i):

max_number = i

return max_number

if __name__ == "__main__":

print(solution(int(input().strip())))

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