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 Common Lisp (SBCL 1.1.14) (judge verdict: Wrong Answer)

(defun solve (n)
  (let ((sq (floor (sqrt n))))
    (loop :for i :from 1 :to sq
          :sum (if (zerop (rem (- n i) i)) (/ (- n i) i) 0))))

(defun main ()
  (format t "~A~%" (solve (read))))

(main)