class Integer
  def divisor_list
    require 'prime'

    return [] if self <= 0
    return [1] if self == 1

    prime_division.map.with_index { |(base, k), i|
      s = i.zero? ? 0 : 1
      (s..k).map { |n| base ** n }
    }.inject { |res, e| res + res.flat_map { |t| e.map { |v| t * v } } }.sort
  end
end

N = gets.to_i
a = (N - 1) * N / 2
ans = 0

N.divisor_list.each do |e|
  ans += e if a % e == 0
end

puts ans