/*╔═══╗──╔╗╔╗───────────────────╔╗────────╔═══╦═══╗
  ║║─║╠╗╠╗╔╣╚═╦══╦═╗╔╦╗╔═╗╔══╦══╣╚═╦╦══╦══╣║─║║║─╚╝
  ║╔═╗║╚╝║╚╣║║║╚╝║║─╔╦╗║║║║╚╝║╚╝║╚╝║║║═╬══║╔═╗║╚╩═║
  ╚╝─╚╩══╩═╩╝╚╩══╩╝─╚╩╝╚╝╚╩══╩══╩══╩╩══╩══╩╝─╚╩═══╝*/

#include<bits/stdc++.h>
using namespace std;

#define f(i,k,n) for(i=k;i<n;i++)
#define fd(i,k,n) for(i=k;i>n;i--)
#define pb push_back
#define mp make_pair
#define ll long long
#define ld long double
#define ull unsigned long long
#define vi vector<int>
#define vll vector<ll>
#define vvi vector<vi>
#define vvll vector<vll>
#define pii pair<int,int>
#define pll pair<ll,ll>
#define mii map<int,int>
#define mll map<ll,ll>
#define all(c) c.begin(),c.end()
#define sz(c) (int)c.size()
#define si(c) (int)c.size()
#define lb lower_bound
#define ub upper_bound
#define gi greater<int>
#define rev reverse
#define ff first
#define ss second
#define yes cout << "YES" << endl
#define no cout << "NO" << endl
#define imp cout << "IMPOSSIBLE" << endl;
#define nl cout << endl
#define hello cout << "hello" << endl;
#define sp(x) fixed << setprecision(x)
#define re return
#define p_q priority_queue

void dbg_out(){cerr << endl;}
template<typename Head, typename... Tail> void dbg_out(Head H, Tail... T) { cerr << ' ' << H; dbg_out(T...); }
#define dbg(...) cerr << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)

const double pi = 3.14159265359;
const ll mod = 1000000007;
const ll modc = 998244353;

ll inline power(ll a, ll b, ll p){
    a %= p;
    ll ans = 1;
    while(b>0){
        if(b & 1)
            ans = (ans*a)%p;
        a = (a*a)%p;
        b >>= 1;
    }
    return ans;
}

ll mod_inv(ll n, ll p){
    return power(n,p-2, p);
}

bool inline isPrime(ll n) {
    if (n <= 1)  return false;
    if (n <= 3)  return true;
    if (n%2 == 0 || n%3 == 0) return false;
    for (ll i=5; i*i<=n; i=i+6)
        if (n%i == 0 || n%(i+2) == 0)
           return false;
    return true;
}
template<typename... T>
void W(T&&... args)
{
	((cout << sp(9) <<  args << " "), ...);
	nl;
}
template<typename... T>
void R(T&&... args)
{
	((cin >> args), ...);
}
ll ston(string s) 
{
	ll a = 0;
	reverse(s.begin(),s.end());
	ll pow = 1;
	for(int i=0;i<s.size();i++)
	{
		a += pow*(s[i]-'0');
		pow*=10;
	}
	return a;
}
template <class T>
string to_binary(T n) 
{
	string binaryNum;
	int i = 0;
	while (n > 0) {
		binaryNum.pb((n % 2)+'0');
		n = n / 2;
		i++;
	}
	reverse(binaryNum.begin(),binaryNum.end());
	return binaryNum;
}
template<class T>
void wv(T &v)
{
	for(auto x : v)
		cout << x << " " ;
	nl;
}
template<class T>
void rv(T &v)
{
	for(int i=0;i<sz(v);i++)
		cin >> v[i];
}
/*
 * USING WITH STRUCT 
   Define a structure .
   Initialize variables in structure.
   Define another structure of type compare.(don't use bool operator < for stl containers (since it is there in std namespace);
   Overload the variables of structure in compare structure.(bool operator()(arguments){} )
   Use container with compare structure. (priority queue me ulta)
*/
/*
      FUNCTIONS YOU ARE USING
    * ll inline power(ll a, ll b, ll p)
    * ll mod_inv(ll n, ll p)
    * bool inline isPrime(ll n) 
    * ll ston(string s)
    * string to_binary(T n)
*/
/* 
 STUFF YOU SHOULD ACTUALLY READ :-
 *int overflow (ll vs int)
 *array out of bounds(runtime errors)
 *special cases (n=1)?
 *don't store large numbers in double(use long double instead)
 *BINARY SEARCH ??
 *in compare return true if you want to place first argument before second argument(p_q me ulta)(bool operator<)(bool operator())
 *do something instead of nothing
*/
void solve()
{
	ll i,j;ll sum = 0,prod = 1;ll maxl = LONG_MIN,minl = LONG_MAX;int maxi = INT_MIN,mini = INT_MAX;
	ll n;
	cin >> n;
	vll v(n+1);
	for(i=1;i<=n;i++)
		for(j=i;j<=n;j+=i)
			v[j]++;
	for(i=1;i<=n;i++)
		sum += i*v[i];
	W(sum);
}
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);
	int t = 1;
//	R(t);
	while(t--)
	{
		solve();
	}
}


Measured memory_bytes: 81272