#include <bits/stdc++.h>
#pragma comment(linker, "/stack:500000000")
#pragma GCC optimize("Ofast")
#pragma GCC target("arch=corei7-avx")
#pragma GCC optimize("-fno-stack-protector")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,abm,mmx,tune=native")
#pragma GCC optimize("-ffast-math")
using namespace std;
const long long MAXN = 1e5 + 7, inf = 1e9, mod = 1e9 + 7;
const long double eps = 1e-17;
long long n, m, a[MAXN], used[MAXN];
signed main() {
  cin >> n;
  long long ans = 0;
  for (long long x = 2; x <= n; x++) {
    for (long long d = 2; d * d <= x; d++) {
      if (x % d != 0) continue;
      ans += x / d * 4;
      if (d * d != x) ans += d * 4;
    }
  }
  cout << ans;
  return 0;
}
