#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

typedef int ll;
typedef unsigned long long ull;
typedef pair<ll, ll> pll;
typedef pair<string, string> pss;
typedef vector<ll> vll;
typedef vector<pll> vpll;
typedef vector<vll> vvll;
typedef vector<vpll> vvpll;
typedef unordered_map<ll, ll> um;
typedef unordered_set<ll> us;

#define fastio ios::sync_with_stdio(false), cin.tie(NULL), cout.tie(NULL);
#define ts ll t; in(t) while (t--) solve();
#define ks ll t; in(t) FOR(i, 1, t+1) out("Case #" << i << ": " << solve());
#define endl '\n'
#define ln cout << endl;
#define in(x) cin >> x;
#define out(x) cout << x << endl;
#define flush cout << flush;
#define reset(a, b) memset(a, b, sizeof(a));
#define ordered_set tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>
#define FOR(i, a, b) for (ll i = a; i < b; ++i)
#define FORI(i, a, b, c) for (ll i = a; i < b; i += c)
#define FORD(i, a, b) for (ll i = a; i > b; --i)
#define FOREACH(it, v, r) for (auto it = v.begin() + r; it != v.end(); it++)
#define FORALL(it, v) for (auto it : v)
#define F first
#define S second
#define mp make_pair
#define pb push_back
#define vin(v, x) vll v(x); FOR(i, 0, x) in(v[i])
#define all(v) v.begin(), v.end()
#define allr(v, r) v.begin(), v.begin() + r
#define showv(v) FORALL(it, v) cout << it << ' '; ln
#define printv(v) FORALL(it, v) out(it)
#define show2d(v) FORALL(it, v) { FORALL(j, it) cout << j << ' '; ln}
#define showm(v) FORALL(it, v) cout << it.F << ": " << it.S << ' '; ln
#define sortv(v) sort(all(v));
#define revv(v) reverse(all(v));
#define maxv(v) *max_element(all(v))
#define minv(v) *min_element(all(v))
#define gcd __gcd
#define checkbit(n, i) (n >> i) & 1               // check ith bit
#define bitcount __builtin_popcount               // count set bits
#define firstbitindex __builtin_ctz               // count trailing zeros
#define lastbitindex __builtin_clz                // count leading zeros
#define bitparity __builtin_parity                // check set bits are even or odd
#define findv(v, x) (find(all(v), x) != v.end())
#define findsm(u, x) (u.find(x) != u.end())
#define findstr(s, x) (s.find(x) != string::npos)
#define sz(a) a.size()
#define precise(x) cout << fixed << setprecision(x);

const ll MAXN = 1e7 + 5, MOD = 998244353, SIZE = 2e7;//, INF = 0x7f7f7f7f7f7f7f7f;
const double EPS = 1e-9, PI = acos(-1);
const int INFi = 0x7f7f7f7f;

//<<------Declare Variables Here----->>//
ll n, min_f, y;
vll spf(MAXN, 2), factors;
long long ans, x;

//<<-----Implement Functions Here---->>//
void sieve()
{
	FORI(i, 3, MAXN, 2)
        spf[i] = i;
    FORI(i, 3, sqrt(MAXN), 2)
        if (spf[i] == i)
            FORI(j, i * i, MAXN, i)
                if (spf[j] == j)
                    spf[j] = i;
}

void solve()
{
	in(n)
	ans = 1;
	for (ll i = 2; i <= n; ++i)
	{
		x = i, min_f = 1, factors = {};
		while (x > 1)
			y = spf[x], x /= y, y > min_f ? factors.push_back(2), min_f = y : ++factors.back();
		x = 1;
		FORALL(it, factors)
			x *= it;
		ans += i * x;
	}
	out(ans)
}

//<<----------Start of Main---------->>//
int main()
{
	fastio
    sieve();
    //ts
    solve();
    return 0;
}

Measured memory_bytes: 42192