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 dPCD1
{
    class Program
    {
        static void Main(string[] args)
        {
            long ans=0L;
            List<long> divisor = new List<long>();
            long N = long.Parse(Console.ReadLine());
            if (N < 3)
            {
                Console.WriteLine(0);
            }else  if (N == 3)
            {
                Console.WriteLine(2);
            }
            else
            {
                for (long i = 2; i <= Math.Sqrt(N); i++) //約数のうち2以上のものを求める
                {
                    if (N % i == 0)
                    {
                        divisor.Add(i);
                        divisor.Add(N / i);
                    }
                }
                divisor.Add(N);

                divisor = divisor.Distinct().ToList();//重複した数を削除した
                foreach (long item in divisor)
                {
                    if (N/(item-1)==N%(item-1))//条件に合うなら、答えに足し込む
                    {
                        ans+=(item-1);
                    }
                }
                Console.WriteLine(ans);
            }
        }
    }
}