function main(input){
	var I = parseInt(input, 10);
	if(I % 2 === 0){
		var a = I / 2;
      	var Ans = a^2;
    }else{
		var a = Mathfloor(I / 2);
      	var A = a+1;
      	var Ans = a * A;
    }
  	console.log(Ans);
}

main(require("fs").readFileSync("/dev/stdin", "utf8"));