#include <iostream>
#include <sstream>
#include <vector>
#include <array>
#include <string>
#include <algorithm>
#include <map>
#include <cmath>
#include <random>

using namespace std;

#define REP(i,first,last) for (int i=first;i<last;++i)
#define MAX(x,y) (x > y ? x : y)
#define MIN(x,y) (x < y ? x : y)

int N;

int main(){
  cin >> N;
  
  long k = N/2;
  long max = (k + 1) * (N - k) + k;

  cout << max << endl;
}