import math

def maxPrimeFactors (n):
	maxPrime = -1

	while n % 2 == 0:
		maxPrime = 2
		n /= 2

	for i in range(3, int(math.sqrt(n)) + 1, 2):
		while n % i == 0:
			maxPrime = i
			n = n / i
	if n > 2:
		maxPrime = n

	return int(maxPrime)



n = 600851475143
print(maxPrimeFactors(n))