#include <bits/stdc++.h>
using namespace std;
const long long int inf = 0x3f3f3f3f;
const long long int mod = 1e9 + 7;
inline long long int add(long long int x, long long int y) {
  x += y;
  if (x >= mod) x -= mod;
  return x;
}
inline long long int sub(long long int x, long long int y) {
  x -= y;
  if (x < 0) x += mod;
  return x;
}
inline long long int mul(long long int x, long long int y) {
  return ((x % mod) * (y % mod)) % mod;
}
inline long long int power(long long int a, long long int b) {
  long long int x = 1;
  while (b) {
    if (b & 1) x = mul(x, a);
    a = mul(a, a);
    b >>= 1;
  }
  return x;
}
inline long long int inv(long long int a) { return power(a, mod - 2); }
const long long int N = 1e5 + 5;
long long int ans[N], p[N];
void sieve() {
  memset(p, 1, sizeof p);
  p[1] = p[0] = 0;
  for (long long int i = 2; i * i < N; i++) {
    if (p[i]) {
      for (long long int j = 2 * i; j < N; j += i) p[j] = 0;
    }
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  sieve();
  long long int n;
  cin >> n;
  for (long long int i = 2; i <= n; i++) {
    if (p[i]) continue;
    for (long long int j = 2; j <= sqrt(i); j++) {
      if (i % j == 0) {
        if (j * j == i) {
          ans[i] += 4 * (i / j);
        } else {
          ans[i] += 4 * (i / j);
          long long int temp = i / j;
          ans[i] += 4 * (i / temp);
        }
      }
    }
  }
  long long int answer = 0;
  for (long long int i = 2; i <= n; i++) answer += ans[i];
  cout << answer;
  return 0;
}
