/**
 *   @FileName	a.cpp
 *   @Author	kanpurin
 *   @Created	2022.01.30 08:22:52
**/

#include "bits/stdc++.h" 
using namespace std; 
typedef long long ll;


int main() {
    int n;cin >> n;
    ll m = (n+1)/2;
    cout << m*(m+1)/2 << endl;
    return 0;
}