>>Sum=(N^3)/6+(N^2)/2+N/3
>>If this is right, I will send you bill ::)
>
>Ladies and gents, we have a winner! That is, converting, the same as my solution of Gifts = n * (n+1) * (n+2) / 6. Congratulations, Edward!

OK, Bruce, you've done it again. It's like a song I can't stop singing in my head.

if my Algebra II memory serves me right, the proper way to write this formula is:

n * (n+1) * (n+2)
-----------------
    (1*2*3)

what kind of problem is this?