28237
 13190
 39914
 81367
 8554
 61106
 67448
 39004
 22308
 16054
 71468
 60501
 100
 300
 59632
 90783
 5611
 1000
 69475
 69753
 10
 5
 582
 8
 36961
 5071
 20
 53213
 92775
 28738
 100000
 92280
 37944
 9
 2627
 7
 3

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#include <bits/stdc++.h>
using namespace std;
void SieveOfEratosthenes(int n, vector<int> &primes) {
  bool prime[n + 1];
  memset(prime, true, sizeof(prime));
  for (int p = 2; p * p <= n; p++) {
    if (prime[p] == true) {
      for (int i = p * p; i <= n; i += p) prime[i] = false;
    }
  }
  for (int p = 2; p <= n; p++)
    if (prime[p]) primes.push_back(p);
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int n;
  cin >> n;
  vector<int> prime;
  SieveOfEratosthenes(n, prime);
  long long ans = 0;
  if (n <= 3) {
    cout << 0 << endl;
    return 0;
  }
  for (int i = 0; i < prime.size(); i++) {
    long long temp = n / prime[i];
    if (temp > 1) {
      temp = (temp * (temp + 1)) / 2 - 1;
      ans += 4 * temp;
    }
  }
  cout << ans << endl;
  return 0;
}
