from math import *
from time import time

start = time()
target = 600851475143
prime_factors = []

for i in range(3, int(sqrt(target)+1)):
	if target % i == 0:
		while target % i == 0:
			target /= i
		prime_factors.append(i)

print(max(prime_factors))
end = time()
print(end - start)
