class-24(1)

#include<bits/stdc++.h>
using namespace std;
const int mx=1e7+123;
#define optimize() ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
long long int cnt[mx];
int main()
{
    //This coding complexity is n ln n but their square root loop will take n sqrt(n);
    optimize();
    int n;
    cin>>n;
    for(int i=1;i<=n;i++)
    {
        for(int j=i;j<=n;j+=i)
        {
            cnt[j]++;
        }
    }
   long long int ans=0;
   for(int i=1;i<=n;i++)
   {
       ans+=(i*cnt[i]);
   }
   cout<<ans;

}