#include <cstring>
#include <cassert>
#include <utility>
#include <iostream>
#include <cstdio>
#include <iomanip>
#include <bitset>
#include <chrono>
#include <cstdlib>
#include <functional>
#include <tuple>
#include <climits>
#include <limits>
#include <deque>
#include <list>
#include <array>
#include <stack>
#include <queue>
#include <random>
#include <complex>
#include <string>
#include <vector>
#include <set>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <algorithm>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

#define ll              long long
#define pi              pair<int,int>
#define pll             pair<ll,ll>
#define pb              push_back
#define F               first
#define S               second
#define vi              vector<int>
#define vll             vector<ll>
#define endl            '\n'
#define all(v)          (v).begin(),(v).end()
#define MP(a,b)         make_pair(a,b)
#define debug(x)        cerr<< #x << " : " << x << endl;
#define debugp(p)       cerr<< #p << " : " << "(" << (p).first << "," << (p).second << ")\n";
#define debugv(v)       cerr<< #v << " : " << "["; for(int i = 0; i < (v).size(); i++) cerr << v[i] << " "; cerr<<"]\n";
#define debugs(m)       cerr<< #m << " : [ "; for(auto itr = m.begin(); itr != m.end(); itr++) cerr <<*itr << " "; cerr << "]\n";
#define debugm(m)       cerr<< #m << " : [ "; for(auto itr = m.begin(); itr != m.end(); itr++) cerr <<"(" << itr->first << "," << itr->second << ") "; cerr << "]\n";

/* ordered set: 
tree<T, null_type,less<T>, rb_tree_tag,tree_order_statistics_node_update>
member functions :
1. order_of_key(k) : number of elements strictly lesser than k
2. find_by_order(k) : k-th element in the set
*/

inline ll modexp(ll x, ll ex , ll md) {
    ll ans = 1ll;
    while (ex > 0) {
        if (ex & 1ll) ans = (ans * x) % md;
        ex >>= 1ll;
        x = (x * x) % md;
    }
    return ans;
}

const int inf = 1e9 + 7;
const int maxn = 1e7 + 9;
ll spf[maxn] , ndv[maxn];

void compute (){
    spf[1] = 1;
    for (int i = 2; i < maxn; i++){
        if (spf[i] == 0){
            spf[i] = i;
            for (ll j = 1ll * i * i; j < maxn; j += i){
                if (spf[j] == 0) spf[j] = i; 
            }
        }
    }

    ndv[1] = 1;

    for (ll i = 2; i < maxn; i++){
        ll t = i;
        ll x = 1;
        while (t != 1){
            ll c = 0;
            ll mdiv = spf[t];
            while (t % mdiv == 0){
                t /= mdiv;
                c++;
            }
            x *= (c + 1);
        }
        ndv[i] = x;
    }

}
void Solve(){
    ll n;
    cin >> n;
    compute ();
    ll ans = 0;
    for (ll i = 1; i <= n; i++){
        ans += i * ndv[i];
    }
    cout <<ans << endl;

}

int main(){
    // ios :: sync_with_stdio(false); 
    // cin.tie(nullptr); 
    // cout.tie(nullptr);
    
    int T = 1;
    // cin >> T;
    for(int tc = 1; tc <= T; tc++){
        // cout << "Case #" << tc << ": ";
        Solve();
    }
    #ifdef LOCAL
    cerr << "Time elapsed\t: " << 1000 * ((double)clock()) / (double)CLOCKS_PER_SEC << "ms\n";       
    #endif
}



Measured memory_bytes: 159868