#include <bits/stdc++.h>
using namespace std;
long long read() {
  char c = getchar();
  bool flag = 0;
  long long x = 0;
  while (c < '0' || c > '9') {
    if (c == '-') flag = 1;
    c = getchar();
  }
  while (c >= '0' && c <= '9') {
    x = (x << 3) + (x << 1) + c - '0';
    c = getchar();
  }
  return flag ? -x : x;
}
int main() {
  long long n = read(), ans = 0;
  for (long long i = 2; i <= n; i++) {
    for (long long j = 2; j * i <= n; j++) ans += j;
  }
  printf("%lld", ans * 4);
}
