using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        int finalAnswer=0;

        List<int> numberList = new List<int>();

        List<int> amicableNumbers = new List<int>();

        for(int i = 2; i < 10000; i++)

            numberList.Add(i);

        //first calculate d(a), also calculate d(b) where b is equal to d(a) and then check if a and b are amicable pairs.

        foreach(int a in numberList)

        {

            //calculate d(a)

            int da = 0;

            List<int> properDivisorsOfA = new List<int>();

            for (int i = 1; i <= a; i++)

            {

                if (a % i == 0)

                    properDivisorsOfA.Add(i);

            }

            properDivisorsOfA.Remove(a);

            foreach(int number in properDivisorsOfA)

                da += number;         //This is d(a)

            //calculate d(b).      // b = d(a)

            int b = da;

            int db = 0;

            List<int> properDivisorsOfB = new List<int>();

            for (int i = 1; i <= b; i++)

            {

                if (b % i == 0)

                    properDivisorsOfB.Add(i);

            }

            properDivisorsOfB.Remove(b);

            foreach(int number in properDivisorsOfB)

                db += number;

            if (da == b && db == a && a!=b)

            {

                amicableNumbers.Add(a);

                amicableNumbers.Add(b);

            }

        }

        foreach (int number in amicableNumbers)

            finalAnswer += number;

        //since every amicable pairs will be duplicated, divide by 2.

        finalAnswer = finalAnswer/2;

        Console.WriteLine(finalAnswer);

    }

}