#coding: UTF-8

import sys
from operator import itemgetter
import re
import itertools
import math

N = input()

if (N%3==0):
	print 3
elif (N%4==0):
	print 4
else:
	while (N%2==0):
		N/=2
	flg = True
	for i in range(3,long(math.sqrt(N)+1)):
		if (N%i==0):
			print i
			flg = False
			break
	if (flg) :
		print N