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# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Diverta
{
    class D
    {
        static void Main(string[] args)
        {
            long N = long.Parse(Console.ReadLine());
            List<long> list = GetAllDivisors(N);

            long sum = 0;
            foreach(long x in list)
            {
                long k = x - 1;
                long a = N / x;
                if (a >= k) continue;
                sum += k;
            }
            Console.WriteLine(sum);
        }

        //全ての約数リストO(√n)
        public static List<long> GetAllDivisors(long x)
        {
            long sx = (long)Math.Sqrt(x);
            List<long> list = new List<long>();
            for (int n = 1; n <= sx; n++)
            {
                if (x % n == 0)
                {
                    long m = x / n;
                    list.Add(n);
                    if (n != m) list.Add(m);
                }
            }
            list.Sort();
            return list;
        }


    }
}