N = int(input())

def prime(n):
    if n == 1:
        return False
    i = 2
    while i * i <= n:
        if n % i == 0:
            return False
        i += 1
    return True

if prime(N):
    print(N)
    exit()
elif N % 2 == 0 and prime(N/2) and N//2 > 2:
    print(N//2)
    exit()

m = 3
while N % m != 0:
    m += 1

print(m)