import math import collections def factorize(n): ''' returns a list of prime factors of n. ex. factorize(24) = [2, 2, 2, 3] source: Rossetta code: prime factorization (slightly modified) http://rosettacode.org/wiki/Prime_decomposition#Python:_Using_floating_point ''' step = lambda x: 1 + (x<<2) - ((x>>1)<<1) maxq = int(math.floor(math.sqrt(n))) d = 1 q = n % 2 == 0 and 2 or 3 while q <= maxq and n % q != 0: q = step(d) d += 1 return q <= maxq and [q] + factorize(n//q) or [n] def sum_of_divisors(n): ''' returns the sum of divisors of integer n. n must be a positive integer. the sum includes n itself. ex. sum_of_divisors(6) = 6 + 3 + 2 + 1 = 12 ''' if n == 1: return 1 factors = collections.Counter(factorize(n)) result = 1 for p, a in factors.items(): result *= (p ** (a + 1) - 1)//(p - 1) return result N = int(input()) if N & 1: print(sum_of_divisors(N)) else: print(sum_of_divisors(N//2))