function Main(input){
var K = input.trim();
K =parseInt(K,10);
var a,b;
if(K%2==1){
  a = Math.floor(K/2);
  b = K - a;
  console.log(a*b);
}else{
  console.log((K*K)/4);
}
}
  Main(require('fs').readFileSync('/dev/stdin','utf8'));

