//#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
#define rep(i, n) for(int i=0; i<n; ++i)
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
using namespace std;
using ll = int64_t;
using ld = long double;
using P = pair<int, int>;
using vs = vector<string>;
using vi = vector<int>;
using vvi = vector<vi>;
const int INF = 100010001;
const ll LINF = (ll)INF*INF*10;


struct Sieve {
    int n;
    vector<int> f, primes;
    Sieve(int n=1):n(n), f(n+1) {
        f[0] = f[1] = -1;
        for(int64_t i=2; i<=n; ++i) {
            if(f[i]) continue;
            primes.push_back(i);
            f[i] = i;
            for(int64_t j = i*i; j <= n; j += i) {
                if(!f[j]) f[j] = i;
            }
        }
    }
    //素数判定
    bool isPrime(int x) {return f[x] == x;}
    //素数判定(1つ用)(宣言はsqrt(x)のサイズで)
    bool isPrime1(int64_t x) {
        bool m = true;
        for(int z:primes) {
            if(!(x%z)) {
                m = false;
                break;
            }
        }
        return m;
    }
    //素数列挙
    vector<int > factorList(int x) {
        assert(x <= n);
        vector<int> res;
        while(x != 1) {
            res.emplace_back(f[x]);
            x /= f[x];
        }
        return res;
    }
    //素因数分解　pair(素数, 素因数の数)
    vector<pair<int, int> > factor(int x) {
        vector<int> fl = factorList(x);
        if(fl.size() == 0) return {};
        vector<pair<int, int> > res(1, pair<int, int>(fl[0], 0));
        for(int p : fl) {
            if(res.back().first == p) {
                ++res.back().second;
            } else {
                res.emplace_back(p, 1);
            }
        }
        return res;
    }
    //素数列挙(1つ用)(宣言はsqrt(x)のサイズで)
    vector<int64_t> factorList1(int64_t x) {
        vector<int64_t> vec;
        for(int z:primes) {
            while(!(x%z)) {
                vec.emplace_back(z);
                x /= z;
            }
        }
        if(x != 1) vec.emplace_back(x);
        return vec;
    }
    //素数列挙(1つ用)(宣言はsqrt(x)のサイズで)　pair(素数, 素因数の数)
    vector<pair<int64_t, int> > factor1(int64_t x) {
        vector<int64_t> vec = factorList1(x);
        vector<pair<int64_t, int> > vecc;
        for(vector<int64_t>::iterator itr = vec.begin(); itr != vec.end(); ++itr) {
            if(itr != vec.begin() && *itr == *(itr-1)) {
                (vecc.end()-1)->second++;
            } else {
                vecc.emplace_back(pair<int64_t, int>(*itr, 1));
            }
        }
        return vecc;
    }
    //約数列挙
    vector<int64_t> div1(int64_t x) {
        vector<int64_t> res(1, 1);
        vector<pair<int64_t, int> > fac = factor1(x);
        for(int i = 0; i < fac.size(); ++i) {
            int si = res.size();
            for(int j = 0; j < fac[i].second; ++j) {
                for(int k = 0; k < si; ++k) {
                    res.emplace_back(res[k+j*si]*fac[i].first);
                }
            }
        }
        sort(res.begin(), res.end());
        return res;
    }
};

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin >> n;
    Sieve pp(10000001);
    ll ans = 0;
    vector<ll> vec(n+1, 1);
    auto prim = pp.primes;
    rep(i, prim.size()) {
        ll num = prim[i];
        if(num > n) break;
        int k = 2;
        while(num <= n) {
            for(ll j = 1; j*num <= n; j++) {
                if(j%prim[i] == 0) continue;
                vec[j*num] *= k;
            }
            num *= prim[i];
            k++;
        }
    }
    rep(i, n) {
        ans += vec[i+1]*(i+1);
    }


    cout << ans << endl;
}

Measured memory_bytes: 125652