#include <bits/stdc++.h>
using namespace std;
const long long mod = 1000000007;
const long long inf = 1e14;
long long gcd(long long a, long long b) { return (b == 0 ? a : gcd(b, a % b)); }
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long n, ans = 0;
  cin >> n;
  for (long long i = 2; i <= n; i++) {
    for (long long j = i + i; j <= n; j += i) {
      ans += (j / i);
    }
  }
  cout << ans * 4;
  return 0;
}
