def solve4():
    n = int(input())
    if n == 1:
        return 0
    li = list(range(1, n + 1))
    lis = [[], []]
    for i in range(0, n // 2):
        lis[i & 1].append(li[i])
        lis[not (i & 1)].append(li[-(i + 1)])
    if n & 1:
        lis[0].append(n // 2 + 1)
    li3 = lis[0] + lis[1][::-1]
    ans = 0
    for i in range(1, n):
        ans += li3[i - 1] * li3[i] + (li3[i - 1] - li3[i])
    return ans + li3[n - 1] * li3[0] + (li3[n - 1] - li3[0])
print(solve4())