#include <bits/stdc++.h>
using namespace std;
long long INF = 1 << 28;
const double pi = acos(-1.0);
int fx[] = {1, -1, 0, 0};
int fy[] = {0, 0, 1, -1};
int dir[4][2] = {1, 0, -1, 0, 0, -1, 0, 1};
const long double EPS = 1e-16;
long long gcd(long long a, long long b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}
long long lcm(long long a, long long b) { return a / gcd(a, b) * b; }
bool cmp(int a, int b) { return a < b; }
struct compare {
  bool operator()(const int& l, const int& r) { return l > r; }
};
int main() {
  int n;
  scanf("%d", &n);
  long long ans = 0;
  for (int i = 2; i <= n; i++) {
    for (int j = i + i; j <= n; j += i) {
      ans += (j / i) * 4LL;
    }
  }
  cout << ans << endl;
  return 0;
}
