import math

N=int(input())

#素数の表の作成
n_sqrt = math.ceil(math.sqrt(N))
isPrime = [True for i in range(n_sqrt+1)]
primes = []
primes.append(2)

for i in range(4,n_sqrt+1,2):
    isPrime[i]=False

#2
if N%2==0:
    N=int(N/2)
    if N%2==0:
        if N%3==0:
            print(3)
        else:
            print(4)
        exit()

#3以上
for i in range(3,n_sqrt+1,2):
    if isPrime[i]==True:
        primes.append(i)
        if N%i==0:
            print(i)
            exit()
        for j in range(i+i,n_sqrt,i):
            isPrime[j]=False
print(N)