#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC target("sse4")
using namespace std;
const long long MAX = -1000000000000000000;
const long long MIN = 1000000000000000000;
const long long inf = 1000000000;
const long long KOK = 100000;
const long long LOG = 30;
const long long li = 500005;
const long long mod = 1000000007;
long long n, m, b[li], a[li], k, flag, t;
long long cev;
string s;
vector<long long> v;
int main(void) {
  scanf("%lld", &n);
  for (long long i = 2; i <= 100000; i++) {
    a[i] = a[i - 1] + i * 4;
  }
  for (long long i = 2; i <= n; i++) {
    cev += a[n / i];
  }
  printf("%lld\n", cev);
  return 0;
}
