It is required to find the number of ways to place NxN K rooks on the chessboard so that they do not attack each other. All rooks are considered equal.
Input
The input file contains natural numbers N and K (\(1 <= N, K <= 8 \)).
Output
Output a single integer - the answer to the problem.
Examples
| # |
Input |
Output |
| 1 |
8 8 |
40320 |