def make_divisors(n):
    divisors = []  #必要に応じてsetにしても良いかも
    i = 1
    while i ** 2 <= n:
        if n % i == 0:
            divisors.append(i)
            if i ** 2 != n:
                divisors.append(n//i)
        i += 1
    #divisors.sort()
    return divisors

N = int(input())
if N % 2 == 0:
    N //= 2
if N == 1:
    print(1)
else:
    print(sum(make_divisors(N)))