#include <bits/stdc++.h>
using namespace std;
const int MAXN = 100000;
const int MAXM = 10000000;
int n, m;
pair<int, pair<int, int>> e[MAXM];
int fa[MAXN + 1];
void init() {
  cin >> n;
  m = 0;
  for (int i = 2; i <= n; i++) {
    for (int j = 2; i * j <= n; j++) {
      e[m].second.first = i;
      e[m].second.second = i * j;
      e[m].first = j;
      m++;
    }
  }
  sort(e, e + m);
}
int findfa(int x) {
  if (fa[x] == x) return x;
  fa[x] = findfa(fa[x]);
  return fa[x];
}
void union_set(int x, int y) {
  int fx = findfa(x);
  int fy = findfa(y);
  if (fx != fy) {
    fa[fx] = fy;
  }
}
void solve() {
  long long ans = 0;
  for (int i = 2; i <= n; i++) fa[i] = i;
  for (int i = m - 1; i >= 0; i--) {
    int u = e[i].second.first;
    int v = e[i].second.second;
    int w = e[i].first;
    if (findfa(u) != findfa(v)) {
      ans += (long long)w;
      union_set(u, v);
    }
  }
  cout << ans * 4 << "\n";
}
int main() {
  cin >> n;
  long long ans = 0;
  for (int a = 2; a <= n; a++)
    for (int x = 2; x * a <= n; x++) ans += (long long)x;
  cout << ans * 4 << "\n";
}
