L = int(input())

cur = 3
count = 0
while(cur <= L):
    count_a = int((L - (cur - 2)) / 2)
#     count_b = int(((L - 2) - (cur - 2)) / 2)
    count_b = count_a - 1
#     print('count_a: {}'.format(count_a))
#     print('count_b: {}'.format(count_b))
    count += (count_a + count_b)
    cur += 2
    
print(count)