#include <bits/stdc++.h>
using namespace std;
#define ll  long long
#define PI  acos(-1)
#define pb  push_back
#define ins insert
#define INF 1000000000000000007 //1e18+7
#define mk  make_pair
#define lb(v,x) lower_bound(all(v),x)
#define ub(v,x)  upper_bound(all(v),x)
#define ff  first
#define ss  second
#define rev reverse
#define endl "\n"
#define max3(x,y,z)  max(x,max(y,z))
#define min3(x,y,z)  min(x,min(y,z))
#define sz(a) (ll)a.size()
#define double long double
#define minpq  priority_queue <ll,vector<ll>,greater<ll> > 
#define coud(a,b) cout<<fixed << setprecision((b)) << (a)
#define fill(x,y)  memset(x,y,sizeof(x))
#define all(x)   (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define bp(n)  __builtin_popcountll(n)
#define mxt(a)  *(max_element(a.begin(),a.end()))
#define mnt(a)  *(min_element(a.begin(),a.end())
#define unique_sort(c) (sort(all(c)), c.resize(distance(c.begin(),unique(c.begin(),c.end()))))
#define rep(i,a,b) for(ll i=(a);i<=(b);++i)
#define trav(a, x) 	  for(auto &a : x)
#define re(i,n)       for(ll i=0;i<n;++i) 
const double eps=1e-7;
const string alpha = "abcdefghijklmnopqrstuvwxyz";
int dx[8]={+1, +1, +1, 0, 0, -1, -1, -1};
int dy[8]={+1, 0, -1, +1, -1, +1, 0, -1};
ll power(ll x,ll y){ll res=1;x=x;while(y>0){if(y&1)res=(res*x);y=y>>1;x=(x*x);}return res;}
ll sqr(ll x) { return x * x;} 
template <typename T> T gcd(T a,T b){ if(a==0) return b; return gcd(b%a,a); }
template <class T> inline void chmax(T &x,T y){ x = max((x), (y));}
template <class T> inline void chmin(T &x,T y){ x = min((x), (y));}
template <class T> T abs(T x) { return x>0 ? x : -x;}
template <typename T> T powm(T a,T b, ll m){T cnt=1; while(b>0){ if(b%2==1) cnt=(cnt*a)%m; b/=2; a=(a*a)%m; }return cnt%m;}
typedef pair<ll,ll>  pii;
typedef vector<pii>  vpii;
typedef vector<ll>   vll;
typedef vector<int>  vii;
ll ncr(ll n,ll r){ll res=1;if(r>n)return 0;if(r>n-r)r=n-r;for(ll i=0;i<r;i++){res*=(n-i);res/=(i+1);}return res;}
const int mod = 998244353;	
const int N = 10000005;
void prec(){
	
}
int spf[N]; 
ll ans; 
// Calculating SPF (Smallest Prime Factor) for every 
// number till N. 
// Time Complexity : O(nloglogn) 
void sieve() 
{ 
    spf[1] = 1; 
    for (int i=2; i<N; i++) 
  
        // marking smallest prime factor for every 
        // number to be itself. 
        spf[i] = i; 
  
    // separately marking spf for every even 
    // number as 2 
    for (int i=4; i<N; i+=2) 
        spf[i] = 2; 
  
    for (int i=3; i*i<N; i++) 
    { 
        // checking if i is prime 
        if (spf[i] == i) 
        { 
            // marking SPF for all numbers divisible by i 
            for (int j=i*i; j<N; j+=i) 
  
                // marking spf[j] if it is not  
                // previously marked 
                if (spf[j]==j) 
                    spf[j] = i; 
        } 
    } 
} 
ll f(int x) 
{ 
	ll cnt=1;
    map <int,int> mp; 
    while(x != 1) 
    { 
        mp[spf[x]]++; 
        x=x/spf[x]; 
    } 
    trav(it,mp){
    	cnt*=(it.ss+1);
    }
    return cnt; 
} 
void run(){
	ll n;
	cin>>n;
	for(int i=1; i<=n; ++i){
		ans+=(f(i)*i*1LL);
	}
	cout<<ans;
}	
int main()
{
    cin.sync_with_stdio(0);cin.tie(0);
	cin.exceptions(cin.failbit);
    int tc=1;
    //cin>>tc;
    prec();
    sieve();
    re(i,tc)
    	run();
    return 0; 
}


Measured memory_bytes: 42716