#include <bits/stdc++.h>
using namespace std;
const long long maxn = 100005;
const long long somod = 1e9 + 7;
long long ans, n, q;
vector<long long> vt[maxn];
int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cin >> n;
  for (long long i = 4; i <= n; i++) {
    for (long long j = 2; j * j <= i; j++) {
      if (i % j == 0) {
        if (j * j == i) {
          vt[i].push_back(j);
        } else
          vt[i].push_back(j), vt[i].push_back(i / j);
      }
    }
  }
  for (long long i = 4; i <= n; i++) {
    {
      for (auto j : vt[i]) {
        ans += i / j * 4;
      }
    }
  }
  cout << ans;
}
