// Divisor Summotary Function
#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define int long long

ll sum(ll l, ll r)
{
    return r * (r + 1) / 2 - l * (l + 1) / 2 + l;
}
ll const N = 100000000;
void Solve()
{
    ll divSum = 0;
    for (int i = 1; i * i <= N; i++) {
        // value <= sqrt(N)
        ll multiplier = N / i;
        divSum += i * multiplier;
        // value > sqrt(N)
        ll NbyA = i; // count
        ll highestVal = N / i;
        ll lowestVal = N / (i + 1) + 1;
        divSum += NbyA * sum(lowestVal, highestVal); // count * sum of values in range
    }
    cout << divSum << '\n';
}

int32_t main()
{
    ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    int t = 1;
    // cin >> t;
    for (int i = 1; i <= t; i++) {
        Solve();
    }
    return 0;
}
// Coded by Tahsin Arafat (@TahsinArafat)