#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int INF = 1e9;
const int MOD = 1e9+7;

int main(void) {
	ll n;cin >> n;
	ll a = n/2,b = n/2+n%2;
	a++;b++;
	cout << a*b-1 << endl;
	return 0;
}