import sys; input = sys.stdin.buffer.readline
sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

#処理内容
def main():
	D = int(input())
	d = int(D // 2)
	if d <= 1:
		print(0)
		return

	if d % 2 == 0:
		ans = int(d // 2) ** 2
		print(ans)
	else:
		ans = int(d // 2) * int(d // 2 + 1)
		print(ans)


if __name__ == '__main__':
	main()