//K-OS WITH THE OCDE

#include<bits/stdc++.h>
using namespace std;
#define ll long long int
#define ff first
#define ss second  
#define ar array
#define mod 1000000007
#define pb push_back
#define mpa make_pair
#define TEST ll t; cin>>t; while(t--)
#define vell vector<ll>
#define vel2 vector<vector<ll>>
#define all(v) v.begin(),v.end()


#define for0(i,n)     for(ll i=0;i<(ll)n;i++)
#define for1(i,n)     for(ll i=1;i<=(ll)n;i++)
#define forr(i,n)     for(ll i=(ll)n-1;i>=0;i--)
#define fall(i,a,b,c) for(ll i=a;i<=(ll)b;i+=(ll)c)

#define db long double
#define endl "\n"
#define MAX INT_MAX
#define MIN INT_MIN

////////////////////////////////////////////////////////////////////////

/*Parity and inversion - ( (grid width odd) && (#inversions even) ) ||
( (grid width even) && ((blank on odd row from bottom) == (#inversions even)) )*/

////////////////////////////////////////////////////////////////////////

ll add(ll a,ll b)  { return ((a%mod+b%mod)%mod); }
ll mult(ll a,ll b) { return (((a%mod)*(b%mod))%mod); }

ll gcdExtended(ll a, ll b, ll *x, ll *y) 
{    
    if (a == 0) {
        *x = 0, *y = 1; 
        return b; 
    }

    ll x1, y1; 
    ll gcd = gcdExtended(b%a, a, &x1, &y1);   
    *x = y1 - (b/a) * x1; 
    *y = x1;  
    return gcd; 
} 

ll modInverse(ll  b, ll  m) 
{ 
    ll x, y; 
    ll g = gcdExtended(b, m, &x, &y); 
    if (g != 1) 
        return -1;   
    return (x%m + m) % m; 
} 

ll modDivide(ll a, ll b, ll m) 
{  
    a = a % m; 
    int inv = modInverse(b, m); 
    return (inv * a) % m; 
} 


ll power(ll a,ll n)
{
    ll ans=1;
    while(n>0)
    {
        ll lastbit=(n&1);
        if(lastbit)
            ans*=a;

        a*=a;
        n>>=1;
    }
   
   return ans;
}
/////////////////////////////////////////////////
int sieveo(ll n) 
{ 
    
    bool prime[n+1]; 
    memset(prime, true, sizeof(prime)); 
    ll ans=0;
   
    for (ll p=2; p*p<=n; p++) 
    { 
        if (prime[p] == true) 
        { 
           
            for (ll i=p*p; i<=n; i += p) 
                prime[i] = false; 
        } 
    } 
  
    
    for (ll p=2; p<=n; p++) 
       if (prime[p]) 
          ans++;
          
          return ans;
}

///////////////////////////////

void primesieve(ll N, ll s[]) 
{ 
    vector <bool> prime(N+1, false); 
  
    for (ll i=2; i<=N; i+=2) 
        s[i] = 2; 
  
    for (ll i=3; i<=N; i+=2) 
    { 
        if (prime[i] == false) 
        { 
            s[i] = i; 
  
             
            for (ll j=i; j*i<=N; j+=2) 
            { 
                if (prime[i*j] == false) 
                { 
                    prime[i*j] = true; 
                    s[i*j] = i; 
                } 
            } 
        } 
    } 
} 

void primefactor(ll N) 
{ 
    
    ll s[N+1]; 
    primesieve(N, s); 

    ll curr = s[N];
    ll cnt = 1;    
    
    while (N > 1) 
    { 
        N /= s[N]; 
        if (curr == s[N]) 
        { 
            cnt++;       
           continue; 
        } 
        
      //curr==prime n.
      //cnt=power
        curr = s[N]; 
        cnt = 1; 
    }
   
}

/////////////////////////////////////////////////////////

void solve()
{
    ll n;
    cin >> n;
    ll sum = 0;
     for(ll i=1 ; i<=n ; ++i) {

         ll x = n/i;
         sum+= (i * (x*(x+1))/2);
     }
     
     cout << sum ;
}

int main()
{
    #ifndef ONLINE_JUDGE
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    #endif
    ios_base::sync_with_stdio(0);cin.tie(0);   
    //TEST
     solve();
}





Measured memory_bytes: 3620