def divisor_list(N): #約数のリスト
    if N == 1: return [1]
    res = []
    for i in range(1,N):
        if i*i >= N: break
        if N%i == 0:
            res.append(i)
            res.append(N//i)
    if i*i == N: res.append(i)
    return sorted(res)

n = int(input())
print(sum(divisor_list(n if n%2 else n//2)))