#include <bits/stdc++.h>
using namespace std;
long long int mn = 1e18;
long long int mx = -1e18;
const long long int mv = 100005;
const double pi = 3.141592653589793238462643;
long long int n, used[mv], res;
vector<long long int> g[mv];
void dfs(long long int v) {
  used[v] = 1;
  for (int i = 0; i < g[v].size(); i++) {
    long long int u = g[v][i];
    res += (max(u, v) / min(u, v));
    if (!used[u]) {
      dfs(u);
    }
  }
}
int main() {
  ios_base::sync_with_stdio(NULL);
  cin.tie(NULL);
  cin >> n;
  for (int i = 2; i <= n; i++) {
    for (int j = i * 2; j <= n; j += i) {
      g[i].push_back(j);
      g[j].push_back(i);
    }
  }
  for (int i = 2; i <= n; i++) {
    if (!used[i]) {
      res = 0;
      dfs(i);
      mx = max(mx, res);
    }
  }
  cout << mx * 2;
}
