def solve():
    N = int(input())
    if N == 1:
        print(0)
        return
    ans = N
    if N % 2 == 0:
        ans += (N // 2) * (N // 2 + 1)
    else:
        ans += (N // 2 + 1) * (N + 1)
    for i in range(N // 2 - 1):
        ans += (i + 1) * (N - i - 1) + (N - i) * (i + 2)
    print(ans)
    return

solve()