// yukicoder: No.80 四角形を描こう
// 2019.5.7 bal4u

#include <stdio.h>

int main()
{
	int D, a, b, ans;

	scanf("%d", &D);
	if (D < 4) ans = 0;
	else if ((D & 3) == 0) a = D >> 2, ans = a*a;
	else {
		a = D >> 2, b = (D - (a<<1)) >> 1;
		ans = a*b;
		a++; b = (D - (a<<1)) >> 1;
		if (a*b > ans) ans = a*b;
	}
	printf("%d\n", ans);
	return 0;
}