// parameter "input" gets all data
function Main(input) {
	// the first line is assigned to input[0], the second line is assigned to input[1] similarly.
	var n = parseInt(input);
	if(n%2==1)
		console.log(parseInt((n-1)*(n+1)/4));
	else
		console.log(parseInt((n*n)/4));
}
// Don't edit this line!
//Main(require("fs").readFileSync(__dirname+'/in.txt', "utf8"));
Main(require('fs').readFileSync('/dev/stdin', 'utf8'));