#include <iostream>
using namespace std;
typedef long long ll;

int main(){
    ll N;
    cin >> N;
    
    ll top = N / 2;
    ll bot = N - top;
    
    ll res = 1;
    res = (res * top);
    res = (res * (bot + 1));
    res = (res + bot);
    
    cout << res << endl;
    return 0;
}