Tetrahedral Numbers
Cannonballs stack in triangular layers: layer k holds k(k+1)/2 balls. Print the total in a stack of N layers.
Input: one integer N.
Output: N(N+1)(N+2)/6.
Constraints:
- 1 ≤ N ≤ 109
Sample Tests
Input 1
3
Output 1
10
Input 2
1
Output 2
1
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