#include <bits/stdc++.h>

namespace DECLARATIONS {
  using namespace std;

  using ll = long long;
  using PI = pair<int, int>;
  template<class T> using V = vector<T>;
  using VI = V<int>;
#define _1 first
#define _2 second

#ifdef MY_DEBUG
# define DEBUG(x) x
#else
# define DEBUG(x)
#endif

  template<class T>
  inline void debug(T &A) {
    DEBUG(
        for (const auto &a : A) {
          cerr << a << " ";
        }
        cerr << '\n';
    )
  }

  template<class T>
  inline void debug_dim2(T &A) {
    DEBUG(
        for (const auto &as : A) {
          debug(as);
        }
    )
  }

  template<typename ... Args>
  inline void debug(const char *format, Args const &... args) {
    DEBUG(
        fprintf(stderr, format, args ...);
        cerr << '\n';
    )
  }

  template<typename ... Args>
  string format(const std::string &fmt, Args ... args) {
    size_t len = std::snprintf(nullptr, 0, fmt.c_str(), args ...);
    std::vector<char> buf(len + 1);
    std::snprintf(&buf[0], len + 1, fmt.c_str(), args ...);
    return std::string(&buf[0], &buf[0] + len);
  }
}
using namespace DECLARATIONS;

const int MOD = 1000000007;

int main() {
  std::ios::sync_with_stdio(false);
  cin.tie(nullptr);

  int N;
  cin >> N;

  auto calc = [&]() {
    ll l = 1, r = N;
    ll ans = l * r;
    for (int i = 2; i < N; ++i) {
      if (i&1) {
        int a = i/2 + 1;
        ans += r * a;
        r = a;
        if (r < l) swap(l, r);
      } else {
        int a = N - i/2;
        ans += l * a;
        l = a;
        if (r < l) swap(l, r);
      }
    }
    ans += l * r;
    return ans;
  };

  if (N == 1) cout << 0;
  else cout << calc();

  return 0;
}