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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (ll i=0; i<(n); ++i)
#define rep1(i,n) for (ll i=1; i<=(n); ++i)
typedef long long ll;
bool debug=false;
string yes = "Yes";
string no = "No";

int main(){
  ll n; cin >> n;
  ll ans=0;
  for(ll p=1;p*p<n; p++){
    if(n%p!=0) continue;
    ll m = n/p -1;
    if(m>p) ans+=m;
  }
  printf("%lld",ans);
  return 0;
}