AT_abc425_a [ABC425A] Sigma Cubes

You are given a positive integer $ N $ . For $ i=1,2,\ldots,N $ , calculate $ (-1)^i \times i^3 $ , and find the sum of these $ N $ values. That is, find $ \displaystyle \sum_{i=1}^N (-1)^i \times i^3 $ .

The input is given from Standard Input in the following format: > $ N $

Output the value of $ \displaystyle \sum_{i=1}^N (-1)^i \times i^3 $ .

### Sample Explanation 1 - When $ i=1 $ : $ (-1)^i\times i^3=-1 $ . - When $ i=2 $ : $ (-1)^i\times i^3=8 $ . - When $ i=3 $ : $ (-1)^i\times i^3=-27 $ . Therefore, output $ -1 + 8 - 27 = -20 $ . ### Constraints - $ N $ is an integer between $ 1 $ and $ 10 $ , inclusive.