main.cc

#include <iostream>
#include <cmath>
#include <cstdlib>
#include <string>

#define let const auto
#define CUBE_COUNT 28

using std::cin;
using std::cout;
using std::endl;
using std::string;

int main()
{
  let func = [](uint n) -> int {
    int ns[3]{0}, swch{0}, cubed{(int)roundf(cbrtf(n * n * n))};

    let mall = [&]() -> int {
      return ns[0] * ns[1] * ns[2];
    };

    while (mall() < n)
    {
      ns[swch]++;
      swch = (swch + 1) % 3;
    }
    if (mall() != n)
    {
      ns[swch == 0 ? 2 : swch - 1]--;
    }

    int
        a = ns[0],
        b = ns[1], c = ns[2],
        res{(a * (b + 1) + b * (a + 1)) * (c + 1) + (b + 1) * (a + 1) * c},
        contcnt{0},
        max_side =
            (a >= b && a >= c) ? a : ((b >= a && b >= c) ? b : c);

    while (mall() + ++contcnt <= n)
    {
      int delta = (contcnt == 1) ? 8 : (((contcnt > 1 && contcnt <= max_side) || (contcnt - 1) % max_side == 0) ? 5 : 3);
      res += delta;
    }
    return res;
  };

  string inp{};
  cin >> inp;
  cout << func(stoi(inp)) << endl;
  return 0;
}