#include<bits/stdc++.h>
using namespace std;
 
#define int             long long
#define ld              long double
#define fi              first
#define se              second
#define pb              push_back
#define mp              make_pair
#define mt              make_tuple
#define fo(i,n)         for(i=0; i<n; i++)
#define fo1(i,n)        for(i=1; i<=n; i++)
#define Fo(i,k,n)       for(i=k; k<=n?i<=n:i>=n; k<=n?i++:i--)
#define all(x)          x.begin(), x.end()
#define rall(x)         x.rbegin(), x.rend()
#define sortall(x)      sort(all(x))
#define sortrall(x)     sort(rall(x))
#define clr(x)          memset(x, 0, sizeof(x))
#define tr(it, a)       for(auto it = a.begin(); it != a.end(); it++)
#define pii             pair<int, int>
#define mk(arr,n,type)  type *arr = new type[n];
#define vi              vector<int>
#define si              set<int>
#define usi             unordered_set<int>
#define mii             map<int, int>
#define umii            unordered_map<int, int>
#define pqmx            priority_queue<int>
#define pqmn            priority_queue<int, vi, greater<int> >
#define setbits(x)      __builtin_popcountll(x)
#define trailzrobits(x) __builtin_ctzll(x)
#define leadzrobits(x)  __builtin_clzll(x)
#define paritybits(x)   __builtin_parityll(x)
#define gcd             __gcd
#define lcm(x, y)       (x * y) / gcd(x, y)
#define mod             1000000007
#define endl            '\n'
#define PI              3.1415926535897932384626
#define inf             1e18
#define sp(x,y)         fixed<<setprecision(y)<<x
void __print(int32_t x) {cout<<x;}
void __print(int x) {cout<<x;}
void __print(ld x) {cout<<x;}
void __print(double x){cout<<x;}
void __print(float x){cout<<x;}
void __print(bool x) {cout<<(x?"true":"false");}
void __print(char x){cout <<'\''<<x<<'\'';}
void __print(const char *x){cout <<'\"' <<x<<'\"';}
void __print(const string &x) {cout<<'\"'<<x<<'\"';}
template<typename T,typename V>     void __print(const pair<T,V> &x) {cout<<'{';__print(x.first);cout<<',';__print(x.second);cout<<'}';}
template<typename T>                void __print(const T &x) {int f = 0; cout << '{'; for (auto &i: x) cout << (f++ ? "," : ""), __print(i); cout << "}";}void _print() {cout << "]\n";}
template <typename T,typename... V> void _print(T t, V... v) {__print(t);if(sizeof...(v))cout<<", ";_print(v...);}
#ifndef ONLINE_JUDGE
#define dbg(x...) cout<<"["<<#x<<"]=[";_print(x)
#else 
#define dbg(x...)
#endif
int power(int base, int exp){ int res = 1; base %= mod; while(exp > 0){ if(exp & 1) res = (res * base) % mod; base = (base * base) % mod; exp = exp >> 1; } return res; }
int inv(int x){ return power(x, mod - 2) % mod; }
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++




const int N = 1e7 + 5, M = N;
int i,j;

void solve(){

    int n; cin>>n;
    vi f(n+1,2);
    f[0]=0, f[1]=1;

    for(int i=2; i<=n; i++){
        for(int j=2*i;j<=n; j+=i){
            f[j]++;
        }
    }

    int sm=0;
    fo1(i,n) sm+=(i*f[i]);
    cout<<sm;
    
    
    
}

int32_t main()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    
    int t = 1;
    // cin >> t;
    while(t--)
        solve();
    return 0;
}

Measured memory_bytes: 81332