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

n = int(input())
if n % 2 == 1:
    f = find_min_factor(n)
    print(f)
else:
    e = 0
    m = n
    while m % 2 == 0:
        m //= 2
        e += 1
    if m == 1:
        print(4)
    else:
        f = find_min_factor(m)
        if e >= 2:
            print(min(4, f))
        else:
            print(f)