#include<bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define FIO ios_base::sync_with_stdio(false);cin.tie(NULL);
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define mt make_tuple
#define ff first
#define ss second
#define vll vector<ll>
#define pll pair<ll,ll>
#define vpll vector<pll>
#define vvll vector<vll>
#define all(v) v.begin(),v.end()
#define itr(r,v) for(auto r=v.begin();r!=v.end();r++)
#define FOR(i,n) for(ll i=0;i<n;i++)
#define ffor(i,a,b) for(ll i=a;i<=b;i++)
#define rfor(i,a,b) for(ll i=a;i>=b;i--)
#define space cout<<"\n\n";
#define endl "\n"
#define pqmx priority_queue<ll>
#define pqmn priority_queue<ll,vll,greater<ll>>
#define fps(x,y) fixed<<setprecision(y)<<x
#define merg(a,b,c) set_union(a.begin(),a.end(),b.begin(),b.end(),inserter(c,c.begin()))
#define set_ar(arr,v) memset(arr,v,sizeof(arr))
#define ctime auto start = high_resolution_clock::now()
#define etime auto stop = high_resolution_clock::now()
#define go_t ll testcases; cin>>testcases; while(testcases--)
#define ptime auto z1z = duration_cast<microseconds>(stop-start); cout<<"Time elapsed : "<<z1z.count()<<" microseconds\n"
#define dbg1(x)             cout <<#x<<": "<<x<<'\n';
#define dbg2(x, y)          cout <<#x<<": "<<x<<" | "<<#y<<": "<<y<<'\n';
#define dbg3(x, y, z)       cout <<#x<<": "<<x<<" | "<<#y<<": "<<y<<" | "<<#z<<": "<<z<<'\n';
#define dbg4(a, b, c, d)    cout <<#a<<": "<<a<<" | "<<#b<<": "<<b<<" | "<<#c<<": "<<c<<" | "<<#d<<": "<<d<<'\n';
#define dbg5(a, b, c, d, e) cout <<#a<<": "<<a<<" | "<<#b<<": "<<b<<" | "<<#c<<": "<<c<<" | "<<#d<<": "<<d<<" | "<<#e<<": "<<e<<'\n';

using namespace std;
using namespace std::chrono;

const ll MOD = 1e9 + 7;
const ll N = 1e6 + 6;
const ll maxN = 1e7 + 5;
const ll MAX_SIZE = 2e6 + 6;
const double PI = 3.14159265359;

ll powerM(ll x, ll y, ll M = MOD) { // default argument
	ll v = 1; x = x % M; while (y > 0) {if (y & 1)v = (v * x) % M; y = y >> 1; x = (x * x) % M;} return v;
}

ll power(ll x, ll y) {
	ll v = 1; while (y > 0) {if (y & 1)v = v * x; y = y >> 1; x = x * x;} return v;
}

vll spf(maxN);
void spfsieve() {
	spf[1] = 1;
	for (ll i = 2; i < maxN; i += 2) spf[i] = 2;
	for (ll i = 3; i < maxN; i += 2) {
		if (spf[i] == 0) {
			spf[i] = i;
			for (ll j = 2 * i; j < maxN; j += i) {
				if (spf[j] == 0) spf[j] = i;
			}
		}
	}
}

int main()
{
#ifndef ONLINE_JUDGE
	freopen("input2.txt", "r", stdin);
	freopen("output2.txt", "w", stdout);
#endif
	FIO
	spfsieve();
	ll n; cin >> n;
	ll ans = 1;
	for (ll i = 2; i <= n; i++) {
		ll temp = 1;
		if (spf[i] == i) {
			ans += (2 * i);
		}
		else {
			ll prev = spf[i];
			ll c = 1;
			ll j = i;
			temp = 1;
			map<int, int> hash;
			while (spf[j] != j) {
				hash[spf[j]]++;
				j = j / spf[j];
			}
			hash[spf[j]]++;
			for (auto it : hash) {
				// cout << it.ff << " " << it.ss << "\n";
				temp = temp * (it.ss + 1);
			}
			// while (spf[j] != j) {
			// 	if (spf[j] == prev) {
			// 		j = j / spf[j];
			// 		c++;
			// 	}
			// 	else {
			// 		temp = temp * (c);
			// 		c = 1;
			// 		j = j / spf[j];
			// 		prev = spf[j];

			// 	}
			// }
			// temp = temp * (c);
			// dbg1(temp);
			ans += (i * temp);
		}
		// dbg1(ans);
	}
	cout << ans;
	return 0;
}


Measured memory_bytes: 81172