#include <bits/stdc++.h>
#define rep(i, n) for(int i=0;i<(int)(n);++i)
#define rrep(i, n) for(int i=(int)(n)-1;i>=0;--i)
#define itr_all(x) (x).begin(),(x).end()
typedef long long lint;
const int INF=1<<29;
const double EPS=1e-9;
using namespace std;


int main (void)
{
  lint n; cin >> n;
  lint sum;
  if(n%2){
    sum = (n/2+1)*(n/2+1)+(n/2);
  }else{
    sum = (n/2+1)*(n/2)+(n/2);
  }
  cout << sum << endl;
  return 0;
}