#include <bits/stdc++.h>
using namespace std;
long long n, ans;
inline int read() {
  char ch = getchar();
  int x = 0, f = 1;
  while (ch < '0' || ch > '9') {
    if (ch == '-') f = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') {
    x = x * 10 + ch - '0';
    ch = getchar();
  }
  return x * f;
}
int main() {
  n = read();
  for (int i = 2; i <= n; i++)
    for (int j = i * 2; j <= n; j += i) ans += j / i;
  cout << ans * 4;
}
