#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int,int>;
const int N = 1e6+10;
int t,n,m,k,l,r,op,x,y;
ll sum = 0;
void solve(){
    cin>>n;
    for(int i = 1;i<=n;i++){
        sum += 1.0L*i*(n/i);
    }
    cout<<sum;
}
int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);  
    solve();
    return 0;
}