# -*- coding: utf-8 -*-
n = int(input())
p = []

for i in range(2,n+1):
    if n%i==0:
        while n%i==0:
            p.append(i)
            p.append(n//i)
            n //= i
    if i*i>n:
        break

p.sort()
for x in p:
    if x>2:
        print(x)
        break