28237
 13190
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 39004
 22308
 16054
 71468
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 300
 59632
 90783
 5611
 1000
 69475
 69753
 10
 5
 582
 8
 36961
 5071
 20
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 100000
 92280
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 2627
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 3

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#include <bits/stdc++.h>
using namespace std;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
long long power(long long a, long long n) {
  a %= 1000000007;
  if (n == 1) return a;
  if (n == 0) return 1;
  if (n % 2)
    return (a * (power((a * a) % 1000000007, n / 2) % 1000000007)) % 1000000007;
  return power((a * a) % 1000000007, n / 2) % 1000000007;
}
const long long inf = (long long)1e18;
long long inverse(long long x) { return power(x, 1000000007 - 2) % 1000000007; }
void solve() {
  long long n;
  cin >> n;
  long long tot = 0;
  for (long long i = 2; i < n / 2 + 1; ++i) {
    tot += ((n - 1) / i) * i;
  }
  cout << 4 * tot << "\n";
}
signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  ;
  long long T = 1;
  for (long long t = 1; t < T + 1; ++t) {
    solve();
    cout << "\n";
  }
  return 0;
}
