n = int(input())

def min_prime_factor(x):
    if x % 2 == 0:
        return 2
    i = 3
    while i * i <= x:
        if x % i == 0:
            return i
        i += 2
    return x

if n % 2 == 0:
    m = n
    while m % 2 == 0:
        m = m // 2
    if m == 1:
        print(4)
    else:
        print(min_prime_factor(m))
else:
    print(min_prime_factor(n))