#include <bits/stdc++.h>
using namespace std;
const int maxn = 1000 * 100 + 100;
long long W = 0;
vector<int> G[maxn];
int seen[maxn];
long long wei[maxn];
void dfs(int u) {
  seen[u] = 1;
  W += 1ll * wei[u];
  for (int i = 0; i < G[u].size(); i++) {
    if (!seen[G[u][i]]) {
      dfs(G[u][i]);
    }
  }
}
int main() {
  int n;
  cin >> n;
  for (int i = 2; i <= n; i++) {
    for (int j = 2 * i; j <= n; j += i) {
      G[i].push_back(j);
      G[j].push_back(i);
      wei[i] += j / i;
      wei[j] += j / i;
    }
  }
  long long ans = 0;
  for (int i = 2; i <= n; i++) {
    W = 0;
    if (!seen[i]) {
      dfs(i);
      ans = max(ans, W);
    }
  }
  cout << ans * 2 << endl;
  return 0;
}
