n = int(input())
nn = 10**6
num = [2]
table = [True] * (nn + 1)

for i in range(2, nn + 1):
    if not table[i]:
        continue
    k = i + i
    while k < nn + 1:
        table[k] = False
        k += i

    num.append(i)

for i in num:
    if i == 2:
        continue
    if n % i == 0:
        print(i)
        exit()
print(n)