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 C (GCC 5.4.1) (judge verdict: Runtime Error)

#include <stdio.h>

long long n, ans;
int main() {
  scanf("%lld", &n);
  for (long long i = 1; i * i <= n; ++ i) {
    if (n % i) continue;
    long long now = n / i;
    if (now - 1 > n / (now - 1))
      ans += now - 1;
  }
  printf("%lld\n", ans);
}