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: Runtime Error)

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

namespace ProblemD
{
    class Program
    {
        static void Main(string[] args)
        {
            var N = long.Parse(Console.ReadLine());
            var minBeforeRount = (Math.Sqrt(4 * N + 1) - 1) / 2.0;
            var min = Math.Ceiling(minBeforeRount);
            var divisors = new List<long>();
            long ret = 0;
            var temp = N;
            for (long i = 2; i * i <= N; i++)
            {
                if (N % i == 0)
                {
                    divisors.Add(i);
                    divisors.Add(N / i);
                }
            }
            divisors.Add(N);
            divisors = divisors.Distinct().ToList();
            divisors.Sort();
            temp = 1;
            foreach(var div in divisors)
            {
                if (N / (div-1) == N % (div-1))
                    ret += div - 1;
            }
            Console.WriteLine(ret);
        }
    }
}