#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <math.h>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <iomanip>
using namespace std;

#define ll long long
#define INF (1 << 30)
#define INFLL (1LL << 60)

int main() {
	unsigned ll n,ans = 0;
	cin >> n;
	if(n % 2 == 0){
		ans = (((n / 2 + 1)) * ((n / 2)));
		ans += (n / 2);
	}else{
		ans = (((n / 2 + 2)) * ((n / 2)));
		ans += (n / 2 + 2);
		ans--;
	}
	cout << ans << endl;
	return 0;
}