#include <iostream>
using namespace std;
int main(){
  int d;
  cin>>d;
  if(d<4){
    cout<<0<<endl;
    return 0;
  } else {
    d/=2;
    int a,b,c;
    a=d/2;
    b=d-a;
    c=a*b;
    int e,f,g;
    e=d/2+1;
    f=d-e;
    g=e*f;
    int x;
    if(c>=g){
      x=c;
    } else {
      x=g;
    }
    cout<<x<<endl;
    return 0;
  }
}