n=input()
if n%3==0:
	print 3
	exit()
if n%4==0:
	print 4
	exit()
for i in xrange(5,int(n**0.5)+2,2):
	if n%i==0:
		print i
		break
else:
	if n%2==0:
		print n/2
	else:
		print n