import java.util.Scanner; public class Main72 { public static void main(String[] args) { Main72 p = new Main72(); } public Main72() { Scanner sc = new Scanner(System.in); long n = sc.nextLong(); solve(n); } public void solve(long n) { long res = ((n/2)) * ((n-n/2)+1) + (n-n/2); System.out.println(res); } }