/* -*- coding: utf-8 -*-
 *
 * 1822.cc:  No.1822 Keima of Shogi - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

/* typedef */

typedef long long ll;

/* global variables */

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d", &n);

  int k = (n + 1) / 2;
  printf("%lld\n", (ll)k * (k + 1) / 2);
  return 0;
}