N = int(input())

# 素数列挙
def prime(x):
    prime = [x if x%2==1 else 2 for x in range(x+1)]
    prime[0] = 1

    for i in range(3, int(x**0.5)+2, 2):
        if prime[i] != i:
            continue   
        for j in range(2*i, x+1, i):
            if prime[j] == j:
                prime[j] = i

    p = {i for i in range(2, x+1) if prime[i] == i}
    return p

p = prime(int(N**0.5)+10)
p = sorted(p)
for v in p:
    if v != 2 and N % v == 0:
        ans = v
        break
else:
    if N % 2 == 0:
        ans = N // 2
    else:
        ans = N
print(ans)