def divisors(n):
    s = [False] * (n + 1)
    s[1] = s[n] = True
    for x in range(2, int(n ** 0.5) + 1):
        if n % x == 0:
            s[x] = True
            y = n // x
            if y != x:
                s[y] = True
    return [i for i in range(n + 1) if s[i]]


def solve():
    N = int(input())

    g = N if N % 2 else N // 2

    print(sum(divisors(g)))


if __name__ == '__main__':
    solve()