/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author champon
 */

//<editor-fold desc="definitions">
#include <bits/stdc++.h>
#define se cout << "test ok" << endl;
#define sp << " " <<
#define enl "\n"
using namespace std;
using ll=long long;
using ld=long double;
using pi = pair<int, int>;
using pl = pair<ll, ll>;
using vi = vector<int>;
using vii = vector<vector<int>>;
using viii = vector<vector<vector<int>>>;
using vl = vector<ll>;
using vll = vector<vector<ll>>;
using vlll = vector<vector<vector<ll>>>;
template<class T> using V = vector<T>;
template<class T> using VV = vector<vector<T>>;
template<class T> using VVV = vector<vector<vector<T>>>;
template<class T1, class T2> using P = pair<T1, T2>;
ll mod = ll(1e9)+7;
ll inf = ll(1e18);
void bl(bool b, ostream& out=cout){ out << (b ? "Yes" : "No") << endl; }
void bl2(bool b, ostream& out=cout){ out << (b ? "YES" : "NO") << endl; }
template<typename T> inline bool chmax(T &a, T b){ if(a<b){a=b; return true;} return false; }
template<typename T> inline bool chmin(T &a, T b){ if(a>b){a=b; return true;} return false; }
int dx[] = {1, 0, -1, 0, 1, -1, 1, -1};
int dy[] = {0, 1, 0, -1, 1, -1, -1, 1};

#ifndef INCLUDE_DEBUG_HPP
#define INCLUDE_DEBUG_HPP

#define TO_STRING(varName) # varName
#include <iostream>
#include <vector>
#include <map>
#include <set>
using namespace std;

namespace dbg {

using ll = long long;

class Debug {
  void prefix() { cout << "\033[7m\033[35m" << " DEBUG " << "\033[0m" << endl; }

  void out_helper(){ cout << endl; }

  void out_with_name_helper(){ cout << endl; }

  template<typename T1, typename... T2>
  void out_helper(T1 v, T2... args);

  template<typename T1, typename... T2>
  void out_with_name_helper(string s, T1 v, T2... args);

  // value
  template<typename T>
  void print(T val);

  // pair
  template<typename A, typename B>
  void print(pair<A, B> p);

  // tuple
  template<typename A, typename B, typename C>
  void print(tuple<A, B, C> t);

  // vector
  template<typename T>
  void print(vector<T> &vec);

  // set
  template<typename T>
  void print(set<T> &st);

  // map
  template<typename A, typename B>
  void print(map<A, B> mp);
public:
  Debug(){}

  template<typename... T>
  void out(T... args){
    prefix();
    out_helper(args...);
  }

  template<typename... T>
  void out_with_name(T... args){
    prefix();
    out_with_name_helper(args...);
  }

  template<typename T>
  void outg(vector<vector<T>> &g) {
    prefix();
    for(auto& v1 : g){
      for(auto& v2 : v1) {
        cout << v2 << " ";
      }
      cout << endl;
    }
  }
};

template<typename T1, typename... T2>
void Debug::out_helper(T1 v, T2... args) {
  print(v); cout << endl;
  out_helper(args...);
}

template<typename T1, typename... T2>
void Debug::out_with_name_helper(string s, T1 v, T2... args) {
  cout << s << ": "; print(v); cout << endl;
  out_with_name_helper(args...);
}

template<typename T>
void Debug::print(T val){
  cout << val;
}

template<typename A, typename B>
void Debug::print(pair<A, B> p){
  cout << "("; print(p.first); cout << ", "; print(p.second); cout << ")";
}

template<typename A, typename B, typename C>
void Debug::print(tuple<A, B, C> t) {
  cout << "("; print(get<0>(t)); cout << ", "; print(get<1>(t)); cout << ", "; print(get<2>(t)); cout << ")";
}

template<typename T>
void Debug::print(vector<T>& vec) {
  cout << "[";
  bool fir = true;
  for(auto& e : vec) {
    if(!fir) cout << " ";
    print(e), fir=false;
  }
  cout << "]";
}

template<typename T>
void Debug::print(set<T> &st){
  cout << "{";
  bool fir = true;
  for(auto& e : st) {
    if(!fir) cout << " ";
    print(e), fir=false;
  }
  cout << "}";
}

template<typename A, typename B>
void Debug::print(map<A, B> mp){
  cout << "{";
  bool fir = true;
  for(auto& p : mp){
    if(!fir) cout << " ";
    print(p), fir=false;
  }
  cout << "}";
}

}

#endif //INCLUDE_DEBUG_HPP

dbg::Debug debug;
//</editor-fold>

#ifndef INCLUDE_FACTOR_HPP
#define INCLUDE_FACTOR_HPP



using namespace std;

namespace factor {

using ll = long long;

class Factor {
public:
  Factor()= default;

  // 素因数分解(Map)
  template<typename T>map<ll, ll> factorMap(T n);

  template<typename T>
  void factorMapAdd(T n, map<T, T> *mp);

  // 素因数分解(Vector)
  template<typename T> vector<ll> factorVec(T n);

  // 約数(Vector)
  template<typename T> vector<ll> divisor(T n);
};

template<typename T>
map<ll, ll> Factor::factorMap(T n) {
  map<ll, ll> res;
  ll buf = n;
  for (ll i = 2; i*i<=n; i++) {
    while (buf % i == 0) {
      res[i]++;
      buf /= i;
    }
  }
  if(buf > 1) res[buf]++;
  return res;
}

template<typename T>
void Factor::factorMapAdd(T n, map<T, T> *mp) {
  ll buf = n;
  for (ll i = 2; i*i<=n; i++) {
    while (buf % i == 0) {
      (*mp)[i]++;
      buf /= i;
    }
  }
  if(buf > 1) (*mp)[buf]++;
}

template<typename T>
vector<ll> Factor::factorVec(T n){
  vector<ll> res;
  ll buf = n;
  for(ll i=2; i*i<=n; i++){
    while(buf%i == 0){
      res.push_back(i);
      buf /= i;
    }
  }
  if(buf > 1) res.push_back(buf);
  return res;
}

template<typename T>
vector<ll> Factor::divisor(T n){
  vector<ll> res;
  for(ll i=1; i*i<=n; i++){
    if(n%i == 0){
      if(i*i == n) res.push_back(i);
      else{
        res.push_back(i);
        res.push_back(n/i);
      }
    }
  }
  return res;
}
}

#endif //INCLUDE_FACTOR_HPP


// verify
// divisor(): https://atcoder.jp/contests/abc161/tasks/abc161_f
factor::Factor fact;

#ifndef DEFINE_MATH_HPP
#define DEFINE_MATH_HPP


using namespace std;

namespace math {

using ll = long long;

class Math {
    ll mod;
public:
  Math(ll mod = 1e9+7):mod(mod){}
  ll keta(ll num);
  ll gcd(ll a, ll b);
  ll lcm(ll a, ll b);
  ll powm(ll num1, ll num2);
  bool isPrime(ll n);
  vector<ll> changeBase(ll n, int b);
};

ll Math::gcd(ll a, ll b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}

ll Math::lcm(ll a, ll b) {
  return a * (b / gcd(a, b));
}

ll Math::keta(ll num) {
  ll k = 0;
  while (num > 0) {
      num /= 10;
      k++;
  }
  return k;
}

ll Math::powm(ll a, ll b) {
  ll res = 1;
  while (b > 0) {
      if (b & 1) (res *= a) %= mod;
      (a *= a) %= mod;
      b >>= 1;
  }
  return res;
}

bool Math::isPrime(ll n) {
  bool flg = true;
  for(ll i=2; i*i<=n; i++){
      if(n%i == 0) {
          flg = false;
          break;
      }
  }
  return flg;
}

vector<ll> Math::changeBase(ll n, int b){
  vector<ll> v;
  while(n > 0){
    ll r = n%b;
    if(r == 0) --n;
    n /= n;
    v.push_back((r-1+b)%b);
  }
  return v;
}

}

#endif //DEFINE_MATH_HPP

math::Math mt;

class DSumOfDivisors {
public:
  void solve(std::istream& in, std::ostream& out){
    ll n;
    in >> n;

    ll ans = 0;
    vl v(10000010);
    for(int i=1; i<=n; i++){
      int cur = i;
      while(cur <= n){
        v[cur]++;
        cur += i;
      }
    }

    for(int i=1; i<=n; i++){
      ans += i*v[i];
    }

    out << ans << endl;
  }
};


int main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  DSumOfDivisors solver;
  std::istream& in(std::cin);
  std::ostream& out(std::cout);
  solver.solve(in, out);
  return 0;
}


Measured memory_bytes: 81336