/*
    @uthor: Amit Kumar
    user -->GitHub: drviruses ; CodeChef: dr_virus_ ; Codeforces,AtCoder,Hackerearth,Hakerrank: dr_virus;
*/
#include <bits/stdc++.h>
#include <chrono>
using namespace std;
using namespace std::chrono;
//#include <boost/multiprecision/cpp_int.hpp>
//namespace mp = boost::multiprecision;
//#define ln mp::cpp_int;
#define int    long long
#define ll long long
#define ld    long double
#define ull   unsigned long long
#define endl "\n"
ll google_itr = 1;
#define google(x) cout<<"Case #"<<x<<":"
#define pi 3.14159265358979323846264338327950L

const ll mod = 1e9+7;
const ll inf = 1e18;
const ll mx = 1e7+2;
ll dp[mx];
ll popcount(ll num){
    num = num - ((num >> 1) & 0x55555555);
    num = (num & 0x33333333) + ((num >> 2) & 0x33333333);
    return ((num + (num >> 4) & 0xF0F0F0F) * 0x1010101) >> 24;
}


void SieveOfEratosthenes(int n, bool prime[], 
                         bool primesquare[], int a[]) 
{ 
    // Create a boolean array "prime[0..n]" and 
    // initialize all entries it as true. A value 
    // in prime[i] will finally be false if i is 
    // Not a prime, else true. 
    for (int i = 2; i <= n; i++) 
        prime[i] = true; 
  
    // Create a boolean array "primesquare[0..n*n+1]" 
    // and initialize all entries it as false. A value 
    // in squareprime[i] will finally be true if i is 
    // square of prime, else false. 
    for (int i = 0; i <= (n * n + 1); i++) 
        primesquare[i] = false; 
  
    // 1 is not a prime number 
    prime[1] = false; 
  
    for (int p = 2; p * p <= n; p++) { 
        // If prime[p] is not changed, then 
        // it is a prime 
        if (prime[p] == true) { 
            // Update all multiples of p 
            for (int i = p * 2; i <= n; i += p) 
                prime[i] = false; 
        } 
    } 
  
    int j = 0; 
    for (int p = 2; p <= n; p++) { 
        if (prime[p]) { 
            // Storing primes in an array 
            a[j] = p; 
  
            // Update value in primesquare[p*p], 
            // if p is prime. 
            primesquare[p * p] = true; 
            j++; 
        } 
    } 
} 
  
// Function to count divisors 
int fac(int n) 
{ 
    // If number is 1, then it will have only 1 
    // as a factor. So, total factors will be 1. 
    if (n == 1) 
        return 1; 
  
    bool prime[n + 1], primesquare[n * n + 1]; 
  
    int a[n]; // for storing primes upto n 
  
    // Calling SieveOfEratosthenes to store prime 
    // factors of n and to store square of prime 
    // factors of n 
    SieveOfEratosthenes(n, prime, primesquare, a); 
  
    // ans will contain total number of distinct 
    // divisors 
    int ans = 1; 
  
    // Loop for counting factors of n 
    for (int i = 0;; i++) { 
        // a[i] is not less than cube root n 
        if (a[i] * a[i] * a[i] > n) 
            break; 
  
        // Calculating power of a[i] in n. 
        int cnt = 1; // cnt is power of prime a[i] in n. 
        while (n % a[i] == 0) // if a[i] is a factor of n 
        { 
            n = n / a[i]; 
            cnt = cnt + 1; // incrementing power 
        } 
  
        // Calculating number of divisors 
        // If n = a^p * b^q then total divisors of n 
        // are (p+1)*(q+1) 
        ans = ans * cnt; 
    } 
  
    // if a[i] is greater than cube root of n 
  
    // First case 
    if (prime[n]) 
        ans = ans * 2; 
  
    // Second case 
    else if (primesquare[n]) 
        ans = ans * 3; 
  
    // Third casse 
    else if (n != 1) 
        ans = ans * 4; 
  
    return ans; // Total divisors 
} 
void pre(){
    for(auto i=0;i<mx+1;i++){
        dp[i]=1;
    }
    for(auto i=2;i<=mx;i++){
        for(auto j=i;j<=mx;j+=i){
            dp[j] ++;
        }
    }
}
 
void virus(){
    pre();
        ll num;
        cin>>num;
        ll sum = 0;
        for(auto i=1;i<=num;i++){
            sum += (i*dp[i]);
        }
        cout<<sum;
}


int32_t main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    
  /*#ifndef ONLINE_JUDGE
    freopen("input.txt","r",stdin);
    freopen("output.txt","w",stdout);
    #endif*/

    ll t=1;
    //cin>>t;
    while(t--){
           auto start = high_resolution_clock::now();
           virus();
           auto stop = high_resolution_clock::now();
           auto duration = duration_cast<seconds>(stop - start);
         //cout << "Time: "<<duration.count()<<endl;
        //your code goes here
    }
    return 0;
}

Measured memory_bytes: 81776