D = int(input())
if D < 4:
    print(0)
else:
    s_even = D if D % 2 == 0 else D - 1
    if s_even < 4:
        print(0)
    else:
        sum_ab = s_even // 2
        a = sum_ab // 2
        b = sum_ab - a
        print(a * b)