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

if n == 4:
    print(4)
    exit()

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)

flag = 0
for i in num:
    if i == 2:
        flag = 1
        continue
    if n % i == 0:
        print(i)
        exit()

if flag:
    print(n//2)
    exit()
print(n)