# your code goes here
#import math
N=int(input())
#Sq=math.sqrt(float (N))
i=3
p=3
while N%i!=0 and i*i<=N:
    i+=1
p=i
if i*i>N:
    if N%2==0 and N>4:
        p=N//2
    else:
        p=N
print (p)