sum of divisors

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
typedef tree<ll,null_type,less_equal<ll>,rb_tree_tag,tree_order_statistics_node_update>ordered_set;
#define suni ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define endl "\n"
#define mn int main()
#define frac() cout.unsetf(ios::floatfield);cout.precision(6);cout.setf(ios::fixed,ios::floatfield);
const int mx=1e7+123;
int a[mx];
mn
{
     suni;
     int n;
     cin>>n;
     for(int i=1;i<=n;i++)
     {
         for(int j=i;j<=n;j+=i)
            a[j]++;
     }
     ll ans=0;
     for(int i=1;i<=n;i++)
        ans+=( 1LL*i*a[i]);
     cout<<ans<<endl;
    }