using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Numerics;
using System.Text;
using static System.Math;

namespace CSharpSpiral {
  class Program {
    public static void Main(string[] args) {
      var sw = new StreamWriter(Console.OpenStandardOutput()) {
        AutoFlush=
#if DEBUG
      true
#else
			false
#endif
      };
      Console.SetOut(sw);
      new Program().Solve(new ConsoleInput(
#if DEBUG
      new StreamReader("../../../inputData.txt")
#else
			Console.In
#endif
      , ' '));
      Console.Out.Flush();
    }
    public void Solve(ConsoleInput cin) {
      var N = cin.ReadInt;
      var count = Enumerable.Repeat(1L, N+1).ToArray();//[i] represents integer i
      count[0]=0;
			for(int i = 2; i<=N; i++) {
        int j = 1;
        while(i*j<=N) {
          count[i*j]++;
          j++;
        }
			}
			Console.WriteLine(count.Select((i,j)=>i*j).Sum());
    }
  }

  static class ExtendClass {
    public static string Join<T>(this IEnumerable<T> X, string separator = " ") => string.Join(separator, X);
    public static int LastOrDefault(this SortedSet<int> S) {
      return S.Any() ? S.Last() : int.MaxValue;
    }
    public static void MergeSort<T>(this T[] A, bool desending) where T : IComparable<T> {
      if(desending)
        MergeSort(A, Comparer<T>.Create((x, y) => y.CompareTo(x)));
      else
        MergeSort(A, Comparer<T>.Create((x, y) => x.CompareTo(y)));
    }
    public static void MergeSort<T>(T[] A, IComparer<T> comparer) where T : IComparable<T> {
      MergeSort1(0, A.Length, A, comparer);
    }
    private static void Merge<T>(int left, int mid, int right, T[] A, IComparer<T> comparer)
      where T : IComparable<T> {
      var nl = mid-left;
      var nr = right-mid;
      var L = new T[nl];
      var R = new T[nr];
      for(int i = 0; i<nl; i++)
        L[i]=A[i+left];
      for(int i = 0; i<nr; i++)
        R[i]=A[i+mid];
      int il = 0, ir = 0;
      for(int k = left; k<right; k++) {
        if(comparer.Compare(L[il], R[ir])<=0) {
          A[k]=L[il++];
          if(il==nl) {
            k++;
            for(; ir<nr;)
              A[k++]=R[ir++];
            break;
          }
        } else {
          A[k]=R[ir++];
          if(ir==nr) {
            k++;
            for(; il<nl;)
              A[k++]=L[il++];
            break;
          }
        }
      }
    }
    private static void MergeSort1<T>(int left, int right, T[] A, IComparer<T> comparer)
    where T : IComparable<T> {
      if(left+1<right) {
        var mid = (left+right)/2;
        MergeSort1(left, mid, A, comparer);
        MergeSort1(mid, right, A, comparer);
        Merge(left, mid, right, A, comparer);
      }
    }
  }
  class ConsoleInput {
    private readonly TextReader _stream;
    private readonly char _separator = ' ';
    private readonly Queue<string> inputStream;
    public ConsoleInput(TextReader stream, char separator = ' ') {
      this._separator=separator;
      this._stream=stream;
      inputStream=new Queue<string>();
    }
    public string Read {
      get {
        if(inputStream.Count!=0) return inputStream.Dequeue();
        string[] tmp = _stream.ReadLine().Split(_separator);
        for(int i = 0; i<tmp.Length; ++i)
          inputStream.Enqueue(tmp[i]);
        return inputStream.Dequeue();
      }
    }
    public string ReadLine { get { return _stream.ReadLine(); } }
    public int ReadInt { get { return int.Parse(Read); } }
    public long ReadLong { get { return long.Parse(Read); } }
    public double ReadDouble { get { return double.Parse(Read); } }
    public string[] ReadStrArray(long N) {
      var ret = new string[N];
      for(long i = 0; i<N; ++i)
        ret[i]=Read;
      return ret;
    }
    public int[] ReadIntArray(long N) { var ret = new int[N]; for(long i = 0; i<N; ++i) ret[i]=ReadInt; return ret; }
    public long[] ReadLongArray(long N) { var ret = new long[N]; for(long i = 0; i<N; ++i) ret[i]=ReadLong; return ret; }
    public double[] ReadDoubleArray(long N) { var ret = new double[N]; for(long i = 0; i<N; ++i) ret[i]=ReadDouble; return ret; }
    public bool isEOF {
      get { return _stream.Peek()==-1; }
    }
	}
}

Measured memory_bytes: 106604