#!/usr/bin/python
def divisors(n):
    sq = int(n ** .5)
    res = ((i, n/i) for i in xrange(1, sq+1) if n%i==0)
    from itertools import chain
    flatten = chain.from_iterable
    return set(flatten(res))

n = int(raw_input())
x = n if n & 1 else n >> 1
res = sum(divisors(x))
print res