#include <bits/stdc++.h>
#include <boost/multiprecision/cpp_int.hpp>
using namespace std;
using bint = boost::multiprecision::cpp_int;
using ll = long long;
using pint = pair<int, int>;
using pll = pair<ll, ll>;
#define rep(i,n) for (int i = 0; i < (n); i++)
#define repSE(i,s,n) for (int i = (s); i < (n); i++)
#define rrepSE(i,s,e) for (int i = (s); i > (e); i--)
#define ssort(v) sort(v.begin(), v.end())
#define gsort(v) sort(v.rbegin(), v.rend())
template<typename T> istream &operator>>(istream &is, vector<T> &vec){ for (auto &v : vec) is >> v; return is; }
template<typename T> ostream &operator<<(ostream &os, const vector<T> &vec){ os << "["; for (auto v : vec) os << v << ","; os << "]"; return os; }
template<typename T> ostream &operator<<(ostream &os, const deque<T> &vec){ os << "deq["; for (auto v : vec) os << v << ","; os << "]"; return os; }
template<typename T> ostream &operator<<(ostream &os, const set<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const unordered_set<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const multiset<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const unordered_multiset<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &pa){ os << "(" << pa.first << "," << pa.second << ")"; return os; }
template<typename TK, typename TV> ostream &operator<<(ostream &os, const map<TK, TV> &mp){ os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; }
template<typename TK, typename TV> ostream &operator<<(ostream &os, const unordered_map<TK, TV> &mp){ os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; }
template<typename T> bool chmax(T &m, const T q) { if (m < q) {m = q; return true;} else return false; }
template<typename T> bool chmin(T &m, const T q) { if (q < m) {m = q; return true;} else return false; }
#define DEBUG_PRINT(var) std::cout << #var << " = " << var << "\n";

struct Sieve {
    int n;
    vector<int> f, primes;
    Sieve(int n = 1):n(n), f(n+1) {
        f[0] = f[1] = -1;
        for(ll i = 2; i <= n; i++) {
            if (f[i]) continue;
            primes.push_back(i);
            f[i] = i;
            for (ll j = i*i; j <= n; j += i) {
                if (!f[j]) f[j] = i;
            }
        }
    }
    bool isPrime(int x) { return f[x] == x;}
    vector<int> factorList(int x) {
        vector<int> res;
        while (x != 1) {
            res.push_back(f[x]);
            x /= f[x];
        }
        return res;
    }
    vector<pint> factor(int x) {
        vector<int> fl = factorList(x);
        if (fl.size() == 0) return {};
        vector<pint> res(1, pint(fl[0], 0));
        for (int p : fl) {
            if (res.back().first == p) {
                res.back().second ++;
            }
            else {
                res.emplace_back(p, 1);
            }
        }
        return res;
    }
    ll ndivs(int x) {
        vector<pint> fl = factor(x);
        ll res = 1;
        for(pint p : fl) {
            res *= (p.second + 1);
        }
        return res;
    }
};

const int MX = 1e7;

int main()
{
    int n;
    cin >> n;
    Sieve si(MX);
    ll ans = 0;
    repSE(i,1,n+1) {
        ans += i * si.ndivs(i);
    }
    cout << ans << "\n";
    return 0;
}


Measured memory_bytes: 46516