Problem:
Score : 500 points

Problem Statement

Snuke received a positive integer N from Takahashi.
A positive integer m is called a favorite number when the following condition is satisfied:

The quotient and remainder of N divided by m are equal, that is, \lfloor \frac{N}{m} \rfloor = N \bmod m holds.

Find all favorite numbers and print the sum of those.

Constraints

All values in input are integers.

1 \leq N \leq 10^{12}

Input

Input is given from Standard Input in the following format:

N

Output

Print the answer.

Sample Input 1

8

Sample Output 1

10

There are two favorite numbers: 3 and 7. Print the sum of these, 10.

Sample Input 2

1000000000000

Sample Output 2

2499686339916

Watch out for overflow.

Solution in Ruby (2.3.3) (judge verdict: Accepted)

N = gets.to_i

ans = 0

d = 1
while d*d <= N
  if N % d == 0
    e = N / d
    if e > 1
      m = e - 1
      x = d
      if m > x
        ans += m
      end
    end
    if d > 1
      m = d - 1
      x = e
      if m > x
        ans += m
      end
    end
  end
  d += 1
end
  
puts ans