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>
int main(){
  long long n,i,j,ans=0;
  scanf("%lld",&n);
  if(n!=2)ans=n-1;
  for(i=2;i*i<n;i++){
    if(n%i)continue;
    j=n/i;
    if(n/(i-1)==n%(i-1))ans+=i-1;
    if(n/(j-1)==n%(j-1))ans+=j-1;//printf("%d\n",ans);
  }
  if(i*i==n){
    if(n/(i-1)==n%(i-1))ans+=i-1;
  }
  printf("%lld\n",ans);
  return 0;
}