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: Accepted)

#include<stdio.h>

#define ll long long

int main(){
  ll N;
  scanf("%lld", &N);
  
  ll sum = 0;
  for(ll i = 1; i * i <= N; i++){
    if(N % i == 0){
      if(i - 1 > N / i) sum += i - 1;
      if(N / i - 1 > i) sum += N / i - 1;
    }
  }
  
  printf("%lld", sum);
  
  return 0;
}