#include <bits/stdc++.h>
using namespace std;
#if __has_include(<boost/multiprecision/cpp_int.hpp>)
	#include <boost/multiprecision/cpp_int.hpp>
	#include <boost/multiprecision/cpp_dec_float.hpp>
	using bll = boost::multiprecision::cpp_int;
	using bdouble = boost::multiprecision::cpp_dec_float_100;
	using namespace boost::multiprecision;
#endif
#if __has_include(<boost/stacktrace.hpp>)
	#define BOOST_STACKTRACE_USE_ADDR2LINE
	#define BOOST_STACKTRACE_ADDR2LINE_LOCATION /usr/local/opt/binutils/bin/addr2line
	#define _GNU_SOURCE 1
	#include <boost/stacktrace.hpp>
#endif
#ifdef LOCAL_TEST
	namespace std {
		template<typename T> class dvector : public std::vector<T> {
		public:
			dvector() : std::vector<T>() {}
			explicit dvector(size_t n, const T& value = T()) : std::vector<T>(n, value) {}
			dvector(const std::vector<T>& v) : std::vector<T>(v) {}
			dvector(const std::initializer_list<T> il) : std::vector<T>(il) {}
			dvector(const std::string::iterator first, const std::string::iterator last) : std::vector<T>(first, last) {}
			dvector(const typename std::vector<T>::iterator first, const typename std::vector<T>::iterator last) : std::vector<T>(first, last) {}
			dvector(const typename std::vector<T>::reverse_iterator first, const typename std::vector<T>::reverse_iterator last) : std::vector<T>(first, last) {}
			dvector(const typename std::vector<T>::const_iterator first, const typename std::vector<T>::const_iterator last) : std::vector<T>(first, last) {}
			dvector(const typename std::vector<T>::const_reverse_iterator first, const typename std::vector<T>::const_reverse_iterator last) : std::vector<T>(first, last) {}
			T& operator[](size_t n) {
				try { return this->at(n); } catch (const std::exception& e) { std::cerr << boost::stacktrace::stacktrace() << '\n'; return this->at(n); }
			}
			const T& operator[](size_t n) const {
				try { return this->at(n); } catch (const std::exception& e) { std::cerr << boost::stacktrace::stacktrace() << '\n'; return this->at(n); }
			}
		};
	}
	class dbool {
	private:
		bool boolvalue;
	public:
		dbool() : boolvalue(false) {}
		dbool(bool b) : boolvalue(b) {}
		operator bool&() { return boolvalue; }
		operator const bool&() const { return boolvalue; }
	};
	#define vector dvector
	#define bool dbool
#endif
#ifdef LOCAL_DEV
	template<typename T> std::ostream& operator<<(std::ostream& s, const std::vector<T>& v) {
		for (size_t i = 0; i < v.size(); ++i){ s << v[i]; if (i < v.size() - 1) s << "\t"; } return s; }
	template<typename T> std::ostream& operator<<(std::ostream& s, const std::vector<std::vector<T>>& vv) {
		s << "\\\n"; for (size_t i = 0; i < vv.size(); ++i){ s << vv[i] << "\n"; } return s; }
	template<typename T> std::ostream& operator<<(std::ostream& s, const std::deque<T>& v) {
		for (size_t i = 0; i < v.size(); ++i){ s << v[i]; if (i < v.size() - 1) s << "\t"; } return s; }
	template<typename T> std::ostream& operator<<(std::ostream& s, const std::set<T>& se) {
		s << "{ "; for (auto itr = se.begin(); itr != se.end(); ++itr){ s << (*itr) << "\t"; } s << "}"; return s; }
	template<typename T> std::ostream& operator<<(std::ostream& s, const std::multiset<T>& se) {
		s << "{ "; for (auto itr = se.begin(); itr != se.end(); ++itr){ s << (*itr) << "\t"; } s << "}"; return s; }
	template <typename T, size_t N> std::ostream& operator<<(std::ostream& s, const std::array<T, N>& a) {
		s << "{ "; for (size_t i = 0; i < N; ++i){ s << a[i] << "\t"; } s << "}"; return s; }
	template<typename T1, typename T2> std::ostream& operator<<(std::ostream& s, const std::map<T1, T2>& m) {
		s << "{\n"; for (auto itr = m.begin(); itr != m.end(); ++itr){ s << "\t" << (*itr).first << " : " << (*itr).second << "\n"; } s << "}"; return s; }
	template<typename T1, typename T2> std::ostream& operator<<(std::ostream& s, const std::pair<T1, T2>& p) {
		return s << "(" << p.first << ", " << p.second << ")"; }
	class SIGFPE_exception : std::exception {};
	class SIGSEGV_exception : std::exception {};
	void catch_SIGFPE([[maybe_unused]] int e) { std::cerr << boost::stacktrace::stacktrace() << '\n'; throw SIGFPE_exception(); }
	void catch_SIGSEGV([[maybe_unused]] int e) { std::cerr << boost::stacktrace::stacktrace() << '\n'; throw SIGSEGV_exception(); }
	signed convertedmain();
	signed main() { signal(SIGFPE, catch_SIGFPE); signal(SIGSEGV, catch_SIGSEGV); return convertedmain(); }
	#define main() convertedmain()
	void debug_impl() { std::cerr << '\n'; }
	template<typename Head, typename... Tail> void debug_impl(Head head, Tail... tail) { std::cerr << " " << head << (sizeof...(tail) ? "," : ""); debug_impl(tail...); }
	#define debug(...) do { std::cerr << "(" << #__VA_ARGS__ << ") ="; debug_impl(__VA_ARGS__); } while (false)
#else
	#define debug(...) do {} while (false)
#endif
//#define int long long
using ll = long long;
//constexpr int INF = (ll)1e9 + 7;//INT_MAX=(1<<31)-1=2147483647
constexpr ll INF = (ll)1e18;//(1LL<<63)-1=9223372036854775807
constexpr ll MOD = (ll)1e9 + 7;
constexpr double EPS = 1e-9;
constexpr ll dx[4] = {1, 0, -1, 0};
constexpr ll dy[4] = {0, 1, 0, -1};
constexpr ll dx8[8] = {1, 0, -1, 0, 1, 1, -1, -1};
constexpr ll dy8[8] = {0, 1, 0, -1, 1, -1, 1, -1};
#define rep(i, n)   for(ll i=0, i##_length=(n); i< i##_length; ++i)
#define repeq(i, n) for(ll i=1, i##_length=(n); i<=i##_length; ++i)
#define rrep(i, n)   for(ll i=(n)-1; i>=0; --i)
#define rrepeq(i, n) for(ll i=(n)  ; i>=1; --i)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
void p() { std::cout << '\n'; }
template<typename Head, typename... Tail> void p(Head head, Tail... tail) { std::cout << head << (sizeof...(tail) ? " " : ""); p(tail...); }
template<typename T> inline void pv(std::vector<T>& v) { for(ll i=0, N=v.size(); i<N; i++) std::cout << v[i] << " \n"[i==N-1]; }
template<typename T> inline bool chmax(T& a, T b) { return a < b && (a = b, true); }
template<typename T> inline bool chmin(T& a, T b) { return a > b && (a = b, true); }
template<typename T> inline void uniq(std::vector<T>& v) { v.erase(std::unique(v.begin(), v.end()), v.end()); }

/*-----8<-----template-----8<-----*/

//MAXVAL以下の素数を求める + MAXVAL以下の整数を素因数分解
//[1-1e7]くらいの範囲で素因数分解をまとめて行いたい場合にお得
constexpr ll MAXVAL = 1e7+1;
constexpr int BITS = (sizeof(int) * 8);
constexpr int FLAGS_NUM = (MAXVAL / BITS + 1);
class Eratosthenes {
public:
	//primes[i] : i番目の素数
	vector<ll> primes;
	//isprime[i] = true:素数, false:合成数
	vector<bool> isprime;
	//min_factor[i] : iに含まれる最小の素因数
	vector<ll> min_factor;
private:
	inline void upflag(int *flags, int BITS, int i) {
		flags[i / BITS] |= 1 << (i % BITS);
	}
	inline int getflag(int *flags, int BITS, int i) {
		return (flags[i / BITS] >> (i % BITS)) & 1;
	}
	inline void setprime(int x) {
		primes.push_back(x);
		isprime[x] = true;
		min_factor[x] = x;
	}
	inline void setcomposite(int x, int factorval) {
		if(min_factor[x] == -1) min_factor[x] = factorval;
	}
	template<typename T1, typename T2> inline T1 power(T1 x, T2 n) {
		return n ? power(x*x,n/2)*(n%2?x:1) : 1;
	}
public:
	Eratosthenes() : primes(), isprime(MAXVAL+1, false), min_factor(MAXVAL+1, -1) {
		int flags[FLAGS_NUM] = {};
		int i, j, f, s;
		int max = (int)sqrt(MAXVAL) + 1;
		setcomposite(0,0);if(MAXVAL<=0)return;
		setcomposite(1,1);if(MAXVAL<=1)return;
		setprime(2);if(MAXVAL<=2)return;
		setprime(3);if(MAXVAL<=3)return;
		for (i = 4; i<=MAXVAL; i+=2) setcomposite(i,2);
		for (i = 9; i<=MAXVAL; i+=6) setcomposite(i,3);
		for (i = 5, f = 4; i <= max; i += (f = 6 - f)) {
			if (!getflag(flags,BITS,i)) {
				setprime(i);
				s = MAXVAL / i;
				for (j = s - !(s & 1); j >= i; j -= 2) {
					if (!getflag(flags,BITS,i)){
						upflag(flags,BITS,i*j);
						setcomposite(i*j,i);
					}
				}
			}
		}
		for (; i <= MAXVAL; i += (f = 6 - f)){
			if (!getflag(flags,BITS,i)){
				setprime(i);
			}
		}
	}

	// n を素因数分解する
	map<ll,ll> prime_factorize(ll n) {
		map<ll,ll> res;
		while (n != 1) {
			ll prime = min_factor[n];
			ll exp = 0;
			while (min_factor[n] == prime) {
				++exp;
				n /= prime;
			}
			res[prime]=exp;
		}
		return res;
	}

	//nの約数を返す　ソートされていないので必要に応じてsort(all(div));してください
	//[1,1e6]ループまでは耐えれるけど、約数の個数だけが知りたい場合は素因数分解の結果から計算してください
	vector<ll> divisor(ll n){
		vector<ll> res;
		map<ll,ll> m=prime_factorize(n);
		ll N=m.size();
		vector<pair<ll,ll>> v(N);
		ll i=0;
		for(pair<ll,ll> pr:m){
			v[i]=pr;
			i++;
		}
		auto f=[&](auto&& f, ll index, ll val){
			if(index==N){
				res.push_back(val);return;
			}
			f(f,index+1,val);
			for(ll i=0; i<v[index].second; i++){
				val*=v[index].first;
				f(f,index+1,val);
			}
		};
		f(f,0,1);
		return res;
	}
};
/*-----8<-----library-----8<-----*/

constexpr ll N_MAX = 1e7;

ll N;

void solve() {
	
	cin >> N;

	/*
	Eratosthenes er = Eratosthenes();
	ll ans = 0;
	repeq(i,N){
		map<ll,ll> t=er.prime_factorize(i);
		ll x=1;
		for(pair<ll,ll> r:t){
			x*=(r.second+1);
		}
		ans+=i*x;
	}

	
	cout << ans << endl;
	*/
	vector<ll> x(N+1,0);
	repeq(i,N){
		for(ll j=i;j<=N;j+=i)x[j]++;
	}
	ll ans=0;
	repeq(i,N)ans+=x[i]*i;
	p(ans);
}

// https://atcoder.jp/contests/abc172/tasks/abc172_d
signed main() {
	solve();
	return 0;
}


Measured memory_bytes: 81392