n = int(input())


p = 2
pmax = int(n**0.5)

num_list = []
while p <= pmax:
	if n % p == 0:
		while n % p == 0:
			n //= p
			num_list.append(p)
	p += 1
	
if n != 1:
	num_list.append(n)


if num_list[0] > 2:
	print(num_list[0])
elif num_list[0] == 2:
	if num_list[1] == 2:
		if 3 in num_list:
			print(3)
		else:
			print(4)
	else:
		print(num_list[1])