#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n; cin >> n;
	if (1 == n) {
		cout << 0 << endl;
		return 0;
	}
	vector<int>v0, v1;
	int l = 1, r = n;
	bool b = true;
	while (l <= r) {
		if (l == r) {
			v0.push_back(l);
			break;
		}
		if (b) {
			v0.push_back(l);
			v1.push_back(r);
		}
		else {
			v1.push_back(l);
			v0.push_back(r);
		}
		l++, r--;
		b ^= 1;
	}
	reverse(all(v1));
	vector<long long>vec;
	rep(i, v0.size())vec.push_back(v0[i]);
	rep(i, v1.size())vec.push_back(v1[i]);
	long long ans = 0;
	rep(i, vec.size()) {
		ans += vec[i] * vec[(i + 1) % n];
	}
	cout << ans << endl;
	return 0;
}