#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1000005;
const long long mod = 1000000007LL;
int n, m, sum0[MAXN];
long long a[MAXN];
int main() {
  cin >> n;
  for (long long i = 2; i * 2 <= n; i++) {
    for (long long j = 2; j * i <= n; j++) {
      a[i * j] += i + j;
    }
  }
  long long ans = 0;
  for (long long i = 4; i <= n; i++) {
    ans += 2 * a[i];
  }
  cout << ans << endl;
  return 0;
}
