n = int(input())
if n == 1:
    print(0)
    exit()

if n % 2 == 0:
    cost = 0
    m = n // 2
    for i in range(1, m):
        cost += i * (n - i)
    for i in range(2, m + 1):
        cost += i * (n - i + 2)
    cost += 1 * n
    cost += m * (m + 1)
else:
    cost = 0
    m = n // 2 + 1
    for i in range(1, m - 1):
        cost += i * (n - i)
    for i in range(2, m):
        cost += i * (n - i + 2)
    cost += 1 * n
    cost += m * (m - 1 + m + 1)

print(cost)