using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Net;

namespace abc172_d
{
  class Program
  {
    static void Main(string[] args)
    {
      var N = CIn.ReadInt();

      var a = new int[N + 1];

      var ans = 0L;

      for (int i = 1; i <= N; i++)
      {
        for (int j = 1; i * j <= N; j++)
        {
          a[i * j]++;
        }
        ans += (long)i * a[i];
      }

      Console.WriteLine(ans);
    }
  }

  static class MathTools
  {
    public static long Gcd(long a, long b)
    {
      while (b != 0)
      {
        var mod = a % b;
        a = b;
        b = mod;
      }
      return a;
    }

    public static long Lcm(long a, long b)
    {
      return a * b / Gcd(a, b);
    }

    public static List<long> PrimeNumbers(long n)
    {
      var list = new List<long>();
      var sieve = new bool[n + 1];

      for (var i = 2; i <= n; i++)
      {
        if (!sieve[i])
        {
          list.Add(i);
          for (var j = i * 2; j <= n; j += i)
          {
            sieve[j] = true;
          }
        }
      }
      return list;
    }

    public static List<long> PrimeFactors(long n)
    {
      var primeNumbers = PrimeNumbers((long)Math.Sqrt(n));
      return PrimeFactors(n, primeNumbers);
    }

    public static List<long> PrimeFactors(long n, List<long> primeNumbers)
    {
      var list = new List<long>();
      var sqrt = (long)Math.Sqrt(n);

      foreach (var p in primeNumbers)
      {
        if (n == 1 || p > sqrt)
        {
          break;
        }
        while (n % p == 0)
        {
          n /= p;
          list.Add(p);
        }
      }
      if (n > 1)
      {
        list.Add(n);
      }
      return list;
    }
  }

  static class CIn
  {
    private static readonly Queue<string> fieldBuffer = new Queue<string>();

    public static string Read()
    {
      if (fieldBuffer.Count == 0)
      {
        foreach (var field in Console.ReadLine().Split())
        {
          fieldBuffer.Enqueue(field);
        }
      }
      return fieldBuffer.Dequeue();
    }

    public static int ReadInt() => int.Parse(Read());
    public static long ReadLong() => long.Parse(Read());
    public static double ReadDouble() => double.Parse(Read());

    public static string[] ReadStringArray(int n)
    {
      var array = new string[n];
      for (var i = 0; i < n; i++)
      {
        array[i] = Read();
      }
      return array;
    }

    public static int[] ReadIntArray(int n)
    {
      var array = new int[n];
      for (var i = 0; i < n; i++)
      {
        array[i] = ReadInt();
      }
      return array;
    }

    public static long[] ReadLongArray(int n)
    {
      var array = new long[n];
      for (var i = 0; i < n; i++)
      {
        array[i] = ReadLong();
      }
      return array;
    }

    public static double[] ReadDoubleArray(int n)
    {
      var array = new double[n];
      for (var i = 0; i < n; i++)
      {
        array[i] = ReadDouble();
      }
      return array;
    }

    public static char[,] ReadCharMatrix(int h, int w)
    {
      var array = new char[h, w];
      for (var i = 0; i < h; i++)
      {
        var l = Console.ReadLine().ToCharArray();
        for (var j = 0; j < w; j++)
        {
          array[i, j] = l[j];
        }
      }
      return array;
    }
  }
}


Measured memory_bytes: 66916